I just graduated from UCSD and I live near downtown, San Diego. La Jolla is a nightmare, so head south. I prefer artsy/dive bars/mom and pop shops- so I live in downtown/Golden Hill.
Hip/Artsy:
Golden Hill (victorian homes, cute coffee shops, eateries, little shops, park overlooking downtown, close to all highways)
South Park (northeast of Golden Hill, lots of cute homes, shops, no freeway access)
North Park (up and coming area, cheaper rent, directly east of Hillcrest and UCSD shuttle)
University Heights (near Hillcrest and UCSD shuttle, quiet gay-friendly community with beautiful homes and shops)
Busy/no car needed:
Hillcrest (shuttle directly to UCSD, bustling/busy gay-friendly neighborhood, very popular amongst UCSD students)
downtown (busy, expensive, and interesting...)
Bankers Hill (north of downtown, lots of homes, small shops, near harbor)
Mission Hills (north of Hillcrest, fun and cute area with a few small shops, overlooks all of downtown and harbor)
Beaches:
Ocean Beach (known to be laid back, hippy friendly, awesome co-op)
Pacific Beach (undergrad party central, a little too manic for me)
Mission Beach (family friendly, mainly vacation rentals)
La Jolla (too expensive and you'll end up driving to all the other areas listed to hangout and get out of La Jolla)
Good luck finding a neighborhood!
Although I felt the student body was a bit stuffy and unfriendly, I did enjoy my undergraduate experience there. They are building a wine bar on campus and have hired the BEST interior designers, so there will soon be plenty of neat hangouts on campus. Other than that, the campus is beautiful- I think you'll enjoy going to UCSD.