Language barriers are really not that bad when travelling. Maybe for me it is second nature, as I grew up with language barriers, and after that, I also spent three years in Africa. Many North Americans have almost no experience dealing with language barriers, as this part of the world has adopted unilingual English to a remarkable degree. But there are strategies to help get through language barriers, just as there are some approaches that seem to make things worse.
It is useful to be aware that some languages are relatively similar. Many Americans and English Canadians tend to lump all foreign languages together, as if it was just as difficult for us to understand French as Chinese. No, that is not true, and with experience, you would find that some languages are really different, others are closer to English and therefore easier to figure out. Also some places are more touristy, and therefore you will have less trouble with a foreign language. As my African high school students remarked to me, (who spoke about 4 languages minimum) they did not really consider French and English different enough to count as two languages. There were 14 native languages in Sierra Leone, a country the size of Southern Ontario, and most of them were not from the same linguistic origin.
I am not trying to suggest you need to be fluent in a language to travel. There are several tips and techniques that work very well, especially in relatively close languages, where tourism is normal.
At the very least, try to learn a few words. Language instructors may not like me letting you in on this secret, but "Hello", and "thank you" are the top two words to know. Probably followed by "Excuse me", "sorry" and "where is the bathroom". If I'm in a language course where I'm being taught "Bellboy, take my bags up to the room, and hurry" then I'm in the wrong course.
Think. All too often, people take their brain offline because they are not confident they will ever figure it out. Consider it like a game, a mystery, a puzzle to solve. Look at all the clues, pay attention to gestures, facial expressions, if possible try to recognize words. Even in Pashtun, I'll bet you hear the occasional English expression. In Timne, the local tribal language in Sierra Leone, one phrase that popped up often enough at school was "Waste time". Anyway, you do need to think more clearly then usual when you are faced with a language barrier.
Try to talk to the right people. With some experience, you will eventually know how to find people who can answer questions, and who it may be best to stay away from. I'm not sure I can help specifically, but I know choosing the right person can make or break the communications. Here is an example. An Internet Cafe in Baja, California. There is no @ sign on your keyboard, because it is a Spanish keyboard. You need help, who to ask, and what do you say? Well don't do what I did and go up to the guy at the front desk and say "Hoy!" thinking it means the same as "Hi!". Hoy actually means "Right now!". "Ola" is hello. A mental lapse on my part. But at least the guy at the desk is going to be a little more understanding than if you blurt this out to someone hard at work typing on another computer somewhere across the room.
Even with a skeleton vocabulary, try to be mindful of what you are saying. If you don't understand the language, it works better to say "Ola" rather than "Como esta", because although both are basically a greeting, "como esta?" is a question (How are you?) that kind of asks for a response, and since you may not be able to understand the response, why ask it in the first place. Of course in real life the interchange usually works itself out, as the other person can usually figure out that you are just a tourist, and you really don't want to know the details of his latest hernia operation. It also might be nice to know the ritual response to "Como esta", which (I think) "Muy bien", because sometimes people may greet you this way.
At any rate, it is obviously not always possible to learn an entire language from scratch for a two-week vacation.
Now here in Canada, the main language "problem" is English and French. Neither the English nor the French see any compelling reason why they must learn the other language, unless they are forced to to get a job (like Prime Minister of the country). But because of our history, a large number of Canadians can speak or understand to some degree the other official language. And, typically, people who are not perfectly bilingual, can understand the other language much better than they speak it. I don't have a full physiological explanation of why this might be, but it is easy to temporarily lose your speaking ability within a year, while your comprehension will last dozens of years without practice.
Up to now I have been considering mainly someone who truly does not understand the language, like me and Spanish.
How are things different when you can understand, but are a bit shy or too tongue tied to speak the other language? Well obviously one problem might be that the other people may think you are just being rude by not speaking when you can obviously understand. I know for sure many English Canadians think this way about French Canadians. I'm sure it is also true in reverse. And in either case, it seems quite easy for, say a French person to be offended when and English person who understands French will not speak in French, and yet at the same time this same French person may have a perfectly good reason why he himself does not need to speak speak English, even though he may understand it pretty well. This double standard is exhibited frequently with both English and French speakers.
When you actually understand the other language, you really must make an extra effort to speak at least the basic words. Again, you don't have to be perfect, but use common sense at all times, pay attention, and keep thinking.
Try to be brief. Reduce what you are saying to what is needed, and no more. Don't bother to launch into an explanation of why you do not speak the language so well, or how slowly they must speak for you to understand them. It wastes time, it causes more misunderstandings. Just say what you need to say, in the other language if you can, if not switch to plain English. I assure you, they will figure out that you do not speak the language, and eventually they will also figure out how slowly they need to speak to you.
Communicate with the aid of hand gestures, or props. For example, buying a fuse for the motorcycle, take the burnt out fuse with you. If your gear shift lever is broken off, take the broken bit with you if at all possible. Pointing helps if you are asking or giving directions. Hand signs are pretty universal, for example, pretending to write on your palm is the international hand sign for "give me the check, please".
Be aware of what emotions are showing on your face. Smile. It works in all languages. Sometimes other facial expressions are called for. This may be important when you are unable to say things like "I am sorry that I'm dripping water all over your new hardwood floor". And even more important when you obviously understand the language, and yet for some reason cannot articulate the word "sorry".
Try to not harbour any negative stereotypes. For example, when a policeman in Mexico asks you how expensive your motorcycle was, don't immediately jump to the conclusion that he is fishing for a bribe. Maybe it is just a natural thing to be fascinated by expensive stuff that would cost them five years salary to buy.
Do not use shouting as a way to overcome a language barrier. And, of course no fist shaking or gun waving.
Do not bother to tell people that you are Canadian. It is irrelevant information, for one thing. I memorized the phrase "Soy Canadense" for when I went to Mexico, and used it on the first waitress I encountered at a restaurant. She gave me a blank stare, so I assumed she could not understand either Spanish or English. Actually, it turned out she understood both, but apparently didn't have a good response to this statement, although maybe she was thinking up some. And in another vein, do not say "Me Canadian, you ????" in a typical Tarzan and Jane movie dialogue.
Get your brain in gear, think of the context, predict what is going to happen. For example, you and two friends walk into a restaurant, a waitress meets you at the door, she probably will ask you "table for three?", it does not matter what the language is. Just nod and follow her to the table, or hold up three fingers. Much better than asking her if she speaks English, or asking her to get an English speaking person for you. Same thing at a military checkpoint. They usually ask the same question, "where are you coming from and where are you heading?" I give them the name of the place I stayed last night, and where I think I may stay tonight. I don't get into anything more complicated, I don't worry too much about exactly what they are saying. One time I got "going to" and "coming from" backwards, and the soldier at the gate looked puzzled and motioned to his commanding officer. He just called back "Inglese?" the soldier nodded, and the officer waved me on. Yes, they can figure stuff out pretty fast. Much much better (and less waiting) than asking people to either speak English or find someone else who can speak English.
Learn the road signs! In Mexico "Curva Peligroso" (hey I still remember that after four years!) means dangerous curve. So then logically, pretty much anything followed by peligroso means "stop text messaging right now!". While it would be helpful to really know what that other peligroso thing might be, don't be looking it up in the phrase book while driving. I might as well mention Vado Peligroso, because it officially means a "dip" in the road, but in Mexico it really means you are crossing a dry river bed. The first five times, you may not even know what the danger is supposed to be, but here are some you will eventually see: Donkey/Cow in the road, hidden in the dip. Road completely under water. Road recently under water, and masses of melon sized rocks are strewn right over the pavement.
And just as importantly, learn that there are no signs at all for some really horrendous stuff, such as half the road was washed way three days ago, or a truck is lying upside down across the entire road (that would probably be in the last five minutes, just judging from how fast the tires are still spinning.)
Sometimes a considerable language barrier exists even in English. Both these incidents happened at the same McDonald's breakfast stop during a motorcycle trip through rural Kentucky (i.e. off the interstate). I went to the counter to order the big breakfast. I really could not understand a word the girl at the cash register said. But she understood "big breakfast and coffee" just fine. When it came out she said "That'll be three thousand dollars". Those were the first words I actually understood! And they were not good. I must have gone blank. Then she laughed and said "I'm joking!" and told me the right price. Actually quite funny, if I had not just got off my motorcycle, and my brain had been given its first coffee yet. Then, sitting down to eat my breakfast a young man came over to my table and launched into a monologue, of which I did not understand one single word. He paused for a bit, while I looked at him. He said "You're not from around here are you?" Finally something I understood. I said "No." He went away, seemingly satisfied with the answer.
In the end, the thing I miss most when there is no language barrier is all the fun you can have when both speak the same language, like I can in Southern Ontario. My two favourites, one when a person is walking a dog, I ask "does your dog bite?" They say "No she's real friendly etc. etc." Then just as I reach down, I stop and say "Is this your dog?" Cracks me up every time. Next, when ordering a "foot long hot dog", (Canada has been a metric country since the early seventies), I ask "how big is is it?". The younger cashiers really struggle with that. I bet some of them don't even know how long a "foot" is, or that it used to be a unit of measure, and not something at the end of your leg
Picture: a military checkpoint. What can you figure out without knowing the words?