Congrats, brother! As a former Angelino, I can say that USD is by far the better choice, as far as life experience will play out. USC is in a crumby part of LA, and Loyola is in such an expensive neighborhood that you would need to commute (unless you are already loaded), and in LA that flat out sucks.
When you get to USD, my only advice is this: Watch out for Ballast Point's Homebrew Mart (a few blocks away). All the HTF Ballast Point stuff is brewed there. And you can't be constantly buying beer and neglecting your books, now can you?
Also, SCB and I (along with a mob of other younger dudes, including a lawyer) all herf every Thursday night a few trolley stops away.
Bienvenidos a San Diego! :smokingme