In North County, San Diego, check out Pacific Coast Cycles in Oceanside. Larry (I think?) who owns the place used to build frames for Masi in Carlsbad, and he's got an incredible selection of old Masi, Cinelli, Colnago, classic Italian stuff, plus a bunch of obscure handmade frames and all the sweet parts you need. The only spot in Northern SD where I could find fixie junk. Anyway, it's an awesome shop, a welcome change from the rich-weekender-wannabe-triathelete bike scene that's so prevalent down here. Coast Highway 101 just as you enter O'side from the South...
And while you're down here go to La Especial Norte in Leucadia for the best Mexican food you'll ever have in your life.