I went to UCSD for undergrad, so I sympathize with your desire to stay in lovely San Diego. I graduated in 2005 and haven't left San Diego... yet. I was just accepted to Hastings as well and am ecstatic to be going there in the fall.
Anyway, if you were accepted to Hastings, you will more than likely be accepted into USD. That being said, I have heard an horror story or two about USD, especially about the incompetence of the administration. I don't know details, so consider this a terrible rumor, but with my limited knowledge, I would say Hastings is the better choice. I can't see going to Hastings limiting your job options in SD in a significant way. And who knows, perhaps you will fall in love with San Francisco and decide to stay. Personally, I think that SD is wonderful, but San Francisco is a dream!
Just my two cents. Hope to see you at Hastings in the fall!