I'm unsure about how I best treat this. My current WIP takes place in a multi-ethnical setting, has people from many nations interacting, which of course would be speaking different languages. The setting is prior to English becoming an international language, yet dialogues are written in English for the sake of the reader. How is something like this solved gracefully? Should I hand out Babel-fishes at the entrance, or simply ignore the issue and hope readers won't think it's weird that they're all able to talk to each other? Now, I come to think of the movie Gladiator. There was a Spaniard, a Nubian, a Carthaginian, a German, etc. all jumbled up in a provincial mud-hole, and they all communicated just fine using English. Is this one of those things we just choose to ignore in fiction? On a slightly different, yet related issue: In a story where none of the characters are actually talking English, the English in their dialogues should probably be seen as some kind of meta-language, and then it would be inappropriate to use any kind of foreign words, at all, right? For example, a character couldn't reply to something saying "Touché!" since that should be auto-translated into "Touch!" given the initial rule. Cheers. (Edited to bring additions up from post below)
Babel Fishes are a plausible idea. Orson Scott Card usually writes all the dialouge in english, and notes what language each speaker is talking in. Either establish that this is just a routine for the diplomats or introduce a couple translating characters.
The three main characters are from different countries, and I can't have translators follow them around throughout the story.
Does your character understand all of the languages being spoken? If so, then it works fine. If not, then I'd suggest only writing the dialogue your character can understand (this is if you're writing in first person or third person limited). Eg: If someone said something to me in German I wouldn't be able to remember/repeat it even a few seconds later as I don't understand it. If they said it in French I could understand them but I wouldn't be able to reply in the same language as I'm not very good at speaking it.
There could be a common language between them (e.g. a trade language or something); or You could have each of them understand bits of pieces of the language of the others; or You could have them ignorant of each other's language and have some magical item or "babel fish" instrument of some kind to help them; or You could have them ignorant of each other's language and use that as part of the conflict of the story - the characters having to deal with a language barrier with no artificial help in addition to whatever else they're dealing with. Any of the above could be done well, just depends on what kind of story you want.
It seems to me that when characters with different native languages are talking to each other, and there's no reasonable expectation that they would know a common language, you need to deal with that issue somehow. Otherwise the reader will be left wondering how that could ever work. Even on Star Trek where everyone conveniently speaks English they wave their hands and say they are wearing "universal translators." It's a nasty hack but it (barely) works given the constraints of the show. Maybe you could take advantage of the linguistic issue by letting the language barrier play some role in character development or even the plot. Maybe one of your MCs is trying to learn one of the other languages and makes some embarrassing or humorous mistakes along the way. How would your MC react to that? How would the other characters react?
Maybe have them all be speaking english but with a few side-conversations when people don't quite understand each other. Logically it could never happen but I feel like it would help at least mention that there is something a little wrong here. Ex: "Do you need help getting to my house for dinner tonight?" "Dinner?" "Dinner. Yeah. Evening meal..." "Oh, like supper?" "Supper?" "It's also an evening meal." Just an idea? Maybe? Or that wouldn't work at all, either way.
Before English was the main language of international commerce, technology, etc, I believe French was the language of diplomacy in Europe. If these people are in a multinational community, there would probably be some sort of lingua franca, though which language/s would depend on the setting.
Unless you want to do the research necessary for period-accurate English, I'd just ignore the issue. If Shakespeare didn't have to care, then neither do you.
And before that, Latin was the international language for all scientists, theologicians and other educated people in Europe, ever since the Roman Empire. Books in science, philosophy and religion were written in Latin, instead of local languages. (Ironically, during the Roman Empire, common people usually spoke Greek, not Latin.) Arabic was the lingua franca of the different peoples on the Arabian peninsula (what we now call the Middle East). In China, educated people could write each other using ideograms (picture-like symbols), even if they spoke different languages. (There's no single language called "Chinese"; the most common Chinese dialect is called "Mandarin").
