depends on what you want to do for work/how willing you are to commute. For instance, I live in Long Beach, and I think it's pretty fantastic. The area around UCLA is super expensive, and USC is in the ghetto. LA is great for food, and there are a shitton of things to do.
Bay area is super cool, but unless if you're making tons of money, you'll probably be living in the East Bay (Oakland, Berkeley, etc.). SF is really nice, and I love visiting there. The whole feel is pretty laid back. I just know I would never be able to afford living in the city.
San Diego is great too. You have pockets with great neighborhood vibes, and the beer is amazing in SD. Plus you're close to TJ if you want to go away for a weekend.
Tons of options. All have pros and cons. Obviously, driving in LA sucks. It takes on average between 30 minutes and an hour to get anywhere. If there's traffic, that time can easily be doubled.