I've lived here for about a year and I'm starting at UH in the fall. I live in Moiiliili, kinda below Manoa and between UH and Waikiki. I'm about a 15 minute bike ride from UH. My boyfriend and I split a 500-sq ft one bedroom for $1200 month; that includes water, cable, and a reserved parking space (if you have a car here, do NOT take a place without parking. parking and traffic in this city are insane). It's a nice place too, recently remodeled with new appliances. Finding apartments pretty much sucks, and you are going to have less space than you do on the mainland, so be prepared for that. The city is small, but for finding cheap housing, Makiki and Moiliili are your best bets. Kaimuki is really nice, with more of a downtown feel to it (the commercial strip along Waialae Ave helps), but it is more expensive and harder to find an apartment. Look in the "shares" section on Craigslist to get a feel for it.
I have a friend who lived on the GA stipend, and he said it was fine, but they definitely weren't rich. He was also splitting costs with his girlfriend, she was working.
I bike almost everywhere I go. A lot of people say it's unsafe, it doesn't really bother me. But I'm used to cycling in crowded cities so YMMV. There is a bike lane on University Ave that goes up to campus, but it cuts straight by a freeway onramp, so I take a back way to get up there through a residential neighborhood.
Honolulu is amazing. There's a lot to do, free or paid. There are also lots of part time jobs to be had (retail, food service) if you need a little extra money.
Let me know if anyone else has questions, I'd love to help if I can.
