I moved to San Diego to start a tech company with a partner about 18 months ago. SD was chosen because partner lived there and was established. We found it very difficult to get the attention of any VC's or potential customers. We did manage to get an interview with YC, but were declined.
Was this due to the location? Perhaps. I do know that the events we went to were lackluster, and the ecosystem was weak. You've got Evonexus (which wouldn't even talk to us), and Connect Springboard, who wanted less complex ideas. Meetups were ok but the ones we went to ended up with more hangers on ("hey I brought my class of 20 HS students to learn about startups at this meetup with 8 people!") than actual people doing stuff.
Also, to be honest I just really didn't like San Diego. My wife got hit by a car while riding to work on a scooter and was in a cast for a few months; the weather was too damn hot (and I lived only two miles from the beach); public transport is dreadful; the culture, while better than LA, is still very socal; drivers tried to kill me as I cycled everywhere; and the city is a model of horrific urban design. Even in places that COULD be great you've got organizations like the Hillcrest Business Association trying to kill a single. damn. bike lane on one of the most heavily-ridden (and dangeous) streets in San Diego - University Ave. The city spends years claiming it's doing something just to have SANDAG kill it. This is particularly egregious when you consider that Todd Gloria supports cycling - until it matters. A bike lane in the middle of nowhere doesn't take any political courage.
SD is vastly overrated. I will admit, though, that the beer and Mexican food are good. Within SD I _did_ quite like South Park. It was when I needed to leave South Park that things were bad.