I keep seeing people saying they got the "Asian" version. Is there more than one IM@S version for the PSP? I thought it wasn't being brought to America?
It's not. There are Japanese and Asian versions of SP. Both are identical except that the Asian version is cheaper.
Also, I have the actual UMD for my PSP. Is there a way to get translations onto it or will I just have to brave it?
I think getting translations onto the UMD would be quite impossible. It might be possible if you had the game on ISO and are using CFW, but this isn't an area I like to tread in.
And are there any full walkthroughs with translations for responses?
Idolmaster, in general, plays out differently for each playthrough, due to varying skill levels of players, the statistics and mood levels of each in-game idol, opponents during each audition, etc.
Of course, there are general tips like when and where to concentrate your efforts on auditions or lessons, but it's extremely difficult to write a step-by-step walkthrough because of all the different factors.
As for answers to communications, there's a site dedicated to providing the information for the 360, PSP and DS games:
http://www.icomu-master.info/No English translations of the communication responses exist as of yet.