I travel a lot for business and spend a ton of time in San Diego, San Francisco, NYC and Austin, TX.
For me, San Diego is tops. Weather is great. People are great. Food, geography, etc and not too crowded. Only issue is that it's like 10 feet from Mexico so you gotta decide if you are cool with that.
San Francisco is cool but the politics drive me nuts - it's prevalent in EVERYTHING. There are times you just want to turn that shit off. Housing - even in places like the East Bay - is stupid expensive.
Central Coast is amazing - St Luis Obispo, Santa Barbara, but you are 2-3 hours from anything.
Austin is the most overrated city on the planet. Yeah, its cool and the food is good and you have insanely hot UT girls, but like San Fran, every asshole walking around looking a hipster bass player for an indie band. And the weather is putrid. You are really trading one extreme for the other. My best friend, who grew up in LaGrange, lives there and basically the kids don't leave the house in the summer - WHEN THEY ARE OFF OF SCHOOL. Think about that. Kids are out of school, but they can't go outside because it's so fucking hot. Trading one extreme for the other. Cool city, but not the be all end all that everyone makes it out to be.
Some cool 'sleeper' cities include Charleston, Savannah, Richmond and even Hunstville.