Goodreads Authors/Readers discussion

The characters in my SF book Vengeance is a Wheel are mostly speaking something I call t-common, which I don't really identify, but I personally think of as 24th Century English. As the author, I also think of myself as writing a translation -- not a direct translation, but a translation into modern idiomatic American English. I remember when the Hercules & Xena TV shows were out thinking these people would be speaking some form of ancient Greek, but the writers are "translating" that to modern idiomatic English.

What do you think? How do you handle language as a part of your work?

Also, I have some parts of the book where the dialogue is in an alien tongue. How do you handle something like this? I'm using footnotes, but that still doesn't feel quite right to me.