In Star Wars everyone speaks is basic, but it's based on an alphabet called Aurebesh - which was created during the production of Empire Strikes Back. It wasn't called English in A New Hope, but that's literally what the universal language was - same rules, same letters, same formatting; lacking a proper name was the only thing different. One of the few decent changes made to the films in their re-releases was changing the English words you can see during A New Hope to Aurebesh. Technically speaking, X-Wings, A-Wings, and B-Wings would be called something completely different if it wasn't translated fo us, as those letters do not appear in the language.
Well to solve such language barriers, all of my Species have learned each others languages out of necessity. When you are thrust in constant conflict with other Species it pays off to learn the language in the long run. This also eliminates the overall need to have lengthy translations, and having to create a language out of thin air. Though I do try to use some of the other Species words to show that they speak a different language.
Basically, I use artificially intelligent head gear when I write. I still have to drop a few days in the book while they attempt an interface with an alien computer but, in the end, the head gear and mouth piece translate the digitized waveforms into a specified and acceptable language. But I also insisted on one complete alien language that has evolved into a dictionary. It's based on root words - with lots of exceptions - and it works for short sections of dialogue. But mostly I rely on the head gear since the alien alphabet has 46 standard sounds and letters. I also created a .tff file for that.
I think highlighting language differences would add a lot of good tension to your setting. Imagine two different soldiers defending a city both their cultures find significant, but they speak totally different languages.
BTW, people who actually do this kind of stuff for a living (moi) cringe whenever we see "universal translator" used in reference to something that automatically interprets speech into another language. Translation is what one does to written items, paperwork, etc. Interpretation is the word for speech. An interpreter interprets for two people who wish to speak to one another but do not speak a common language. A translator translates documents from one language to another.
If their universe contains magic, then that could handle the translation aspect. The magic of the portal they use could change them in such a way that they know how to speak the native tongue of their destination automatically. As others have said though, you probably don't have to explain this point in the book itself, although I've always thought it's good to have an explanation figured out for your own reference, just so that things stay internally consistent in the future.
Look to history for an explanation that might help. In the past traders would need to learn many languages if they dealt in places with different languages, but overall you speak what is necessary to live in a spot. So, if your races are 'mixing' often, they might use a Lingua Franca. However, many fantasy books don't need to address this, since it is accepted that we are reading a story. Unless you say explicitly that they speak English, you probably don't need to bother with explaining things away. Unless you want to get monstrously complex. And elvish. So much elvish.
You should probably at least hang a lampshade on it ("Huh, how come everyone speaks English? Weird.") - but it's not difficult to find sci-fi where everyone can understand eachother with absolutely no explanation. Hell, the Stargate franchise drops the idea of having to translate other languages after about 2 episodes, and ten seasons go by in which even alien peasants from other galaxies speak fluent English (with an American accent, no less) and nobody bats an eyelid. Without more information about your setting, it's not easy to suggest an option, but there's a good range of them; Doctor Who's TARDIS psychic translation matrix, Farscape's translator microbes, even The Simpsons' "by an astonishing coincidence both languages are exactly the same". If your universe has a fairly well established galactic community (e.g. Star Wars) you could even just claim that everyone is at least reasonably fluent in a single "common" language.
Have any authors used the Rosetta Stone concept for their sci-fi language problem. I am thinking along the lines of the obelisk in 2001 sort of thing. Historically the British sea faring abilities have made English one of the most known languages worldwide, maybe an ancient alien race could leave a Rosetta Stone behind in all the places they visit that is only visible/discoverable through advance science techniques that generally foreshadow space travel so a universal communication method presents itself.