LA is a huge city - a huge, sprawling city, from what I've heard. I've lived in the Philly area my whole life, and we have our share of neighborhoods, but the ideal places to live are fairly concentrated and everything is well connected by public transportation anyway, so you're never too far from downtown.
So where to start looking for someone that knows nothing about LA? Especially if you don't want a long commute? Westwood and Brentwood seem obvious since they're close to campus. But what if you don't want to live next to a frat house? What's the deal with the 405? I've heard nightmare stories (the notion of the upcoming "Carmageddon" is comical to me). So I asked my second year buddy match and got some great advice (thanks Tim!)
The majority of people live west of the 405 between Barrington and Bundy to the west and east and Santa Monica and San Vicente to the south and north. It's an ideal location because it's a short commute to campus (getting across the 405 is a pain but east of the 405 is where most of the undergrads and grad students without cars live), it's close to the bars that Anderson students go to most (Q's and Cabo), and it's convenient to go west into Santa Monica. Coming from santa monica is more of a congestion issue. If you don't mind a 45-ish min commute then it's doable, but it's more like 15-20mins from Brentwood.