We have a (human) character from a fairly ordinary background who gets dragged off to strange and interesting places. Logically, the (also human) people in the strange and interesting places would not speak the same language. But these characters need to be able to communicate -- have conversations, even -- because otherwise it's all very boring.
Which of the following solutions to this problem do you find acceptable?
Ignore It: Just avoid the question entirely. Everyone speaks 'English' and language is simply never mentioned.
Gloss Over It: Acknowledge briefly how strange it is that everyone speaks 'English', but provide no explanation.
Translator Microbes: Describe a whatchamajigger that solves the problem, but don't explain how it works.
Babel Fish: The whatchamajigger is explained in a hand-wavy way, then we move on.
Universal Translator: Whatchamajigger with explanation; how it works is sometimes plot-relevant.
Fast Learning: Invoke technobabble to let characters absorb new languages very quickly.
The Low-Tech Way: Characters learn new languages through conveniently-available months of intensive study.
Other: some exciting and clever method I haven't thought of, which is described in a comment.