Adams Ave is great, my favorite LBS is Cal Coast, right down the street (on Adams).

Will you also be living in LJ? There is a University Cycling; I can't remember its exact name but it is up in La Jolla near the Whole Foods. B + L Bikes is excellent, they specialize in Specialized and do a shop ride from their North County location.

There are a few centuries a year here; you'll be arriving in time for the Tour de Poway which is excellent; starts off with a nice bit of climb. There's a San Diego Century, but I've never ridden any part of it, it conflicts with a Los Angeles ride that I love. Lots of riders here train for the Solvang Century, a couple of hours up the road, and there is a Palm Springs century in Feb that is popular.

There is a Luna Chix group of women riders that I have heard good things about.

For MTB there is Noble Canyon and Mission Trails in the city and a bit farther out of town Mount Laguna has fun trails.

We have a San Diego Bike Coalition that will provide a bunch of info for you as well as a SD chapter of the Mountain Bike association.