What is with all this talk about gangs?!?! It's not like there are thugs on every corner waiting to shoot you. I think maybe you guys have lived in the city too long! You're going to give the guy the wrong impression.
The exception might be LA. LA sucks. Smog, idiots, crime, idiots, traffic, and idiots.
SD, LA and SF have 1 good thing going for them, you can go surfing, skiing, and off roading in 1 day if you really wanted to. The central coast, like Santa Barbara and San Luis Obispo (like where slosurfer lives) is really nice.