Was born and raised in San Diego and I love it. I would never say I would NEVER move, or live, anywhere else, but close, you know.
There are nice places everywhere, and exceptions to the rules always, but you'd probably want to be in the more coastal areas, avoid South Bay, East County, and North County for the most part. I live Downtown, but Fashion Valley is nice, North Park, South Park, Coronado, La Jolla, of course. Almost everything I want is close, the beach, Downtown, which is clubs, bars, restaurants, Little Italy, 10 min from Fashion Valley, which if you're into clothes/shoes is one of the better places, on the west coast. Then you have the beaches, museums, art galleries. Here, you can surf in the summer, snowboard in the winter, it's like an hour and a half away. Women. It's expensive though, but I have never lived elsewhere, so it's all I know. Esp. compared to midwest, or down south. Rent, likely won't be cheap, in most of the above mentioned areas. Low is about 800. High about 1800, one bedrooms.
Negatives? High unemployment right now, I believe, hard to find jobs, probably, and then the usual stuff for every city, esp. major ones, homeless, lower socioeconomic neighborhoods. But, not much negative I can say.