The campus is very centralized and compact. All the buildings and classes you'd ever use are all within the "compound." Getting around the immediate campus is a breeze. There are trams and cars that can transport you within the student filled area 24/7. If you google map.... the general area where all students are is bordered by figueroa/adams/vermont on the north, and the more quiet but "spooky" west side by exposition/normandie/jefferson. Anything within this region is filled with students and not bad at all. I'd say the danger of the area is very overhyped. It's not the prettiest part of town, but theres no reason to fear for your life. (Even though they can be annoying, I like the fact that the campus police probably have more liberty to shoot a thug than the real police.) It really is like an oasis though.
Nevertheless... LA is a car town, the car is indispensible. Campus won't be an issue, but if you want to see the rest of LA a car is recommended. It is amazing at just how much you can do and see just a short trip away though. USC is so centralized, you can go to Beverly Hills, Santa Monica, Malibu, Pasadena, Hollywood, Burbank, Long Beach, Downtown, etc etc all within 25 minutes (pending traffic).
Yea, undergrad and grad seem to lead different lives. There shouldn't be anything stopping you from joining in all the undergrad activities though.
whodini's price ranges are spot on. It's hard, but try to find that landlord who won't screw you.
johnapril- Spudnuts is tasty, but was this burrito place Chanos? or the place right next door which is really good (probably newer than 93 though). I try to reserve Chano's for extremely drunken indulgences