Okay, I haven't written anything on this site for quite some time now, but I just felt I should contribute to this post, since there seems to be a lot of misinformation.
USC Health Science Campus is not really near the Main Campus. There is a shuttle between the two. I currently work at USC-HSC and I live in Pasadena, right beside Cal Tech. It takes me 20 minutes -no freeway- to get there, and then another 5-10 to park and get to the door of my lab. My fiance has just started his fourth year of med school at USC, so I have had a chance to find out where most med students live. The majority live in either: El Sereno -the closest, least expensive, but not the nicest; Monterey Hills -a lot of students live here - the apartments are very new and nice, and it is also very close to the school; the only problem is that there is quite a bit of car theft/break-ins, especially if you park on the street; most apartments have gated parking; the prices vary but are on the higher end and you almost definitely have to share a place with one or two other people; South Pasadena -a very nice, posh, family-oriented neighborhood where many of the faculty live; it is expensive and the apartments are quite old; it is about a 15 min drive into USC-HSC; Pasadena -which is just north of South Pas, and has a wide variety of prices from cheap to outrageous - think Paseo Colorado luxury apartments: $2000/mo. Our rent is $1000 for a two bed, two bath, and we're quite happy with it since we can walk to South Lake and shops on Colorado Blvd, Alhambra is somewhat east and northeast of campus, and also has its share of nice and not-so-nice areas. The northern part is very nice, family neighborhoods, borders South Pasadena. The southern part is along the 10 Fwy, where there is a predominantly Asian community -lots of great food - Monterey Park is a little bit south of Alhambra, and is also predominantly Asian, and there are some nice condo-style apartments for reasonable prices here. Both are about 10-15 minutes away. None of the places I have listed require you to drive the freeways.
From my observations, the majority of students live in Monterey Hills or South Pasadena -the closest, followed by Pasadena and Alhambra. I've lived in South Pasadena, and it is very nice and convenient, but old and expensive. I really like where I live now.
There is indeed a dorm on campus -Seaver, but it is not really ideal since you can't go anywhere without a car anyways. of course, there is something to be said for rolling out of bed and walking 50 paces to class.
And for those of you who are interested in the west side of Los Angeles, be aware that the traffic will be terrible. The only students I know who live in west L.A. are the ones who went to UCLA and like the atmosphere there and are willing to commute. Los Feliz is fairly close and is a hip and happening place, but can put a strain on your wallet. Glendale and Eagle Rock are alternatives that are not so expensive and have some nice places as well. They are a bit farther, and may require some freeway driving.
In all honesty, the majority of people I know live pretty nearby - 8am classes can be a drag - mostly where I mentioned above.
Good luck for those of you who are looking.
-ln