For women's middle distance running, UC-Irvine is a very solid bet. Their coach is a good egg, a lot of runners drop in to train over the breaks, and he has substantial knowledge and the results to show for it. I trained down there with a couple of Pac-10 runners over X-mas break one year in the 1980s but am blanking on his name at the moment. I also have a friend in LA who knows him, but he is more of a 10K to marathon type. E-mail me and I can put you in touch with him. They work out a few days a week.
San Diego - you might try Marc Davis aka The DOC. I have his e-mail too if you need it. He's new to coaching and some folks on the board like to rile him, but he has a lot of hands-on race experience and seems to have matured. Great place to train year-round, but the road/club scene is not all it's cracked up to be so you'll want to find a coach there who works with college-level runners or better. Marc should be able to plug you into a good environment, plus there is the Chula Vista/ARCO U.S. Olympic Training Center you may be able to avail yourself of.
Boulder - this is more of a 5K/10K/'thoner town. There is not as much across the board (compared to its international reputation) in the way of female middle-distance running but I know of a few gals who run well here, notably the Colorado Elite Track Club with Shayne Culpepper, Janet Trujillo, Carrie Messner, Shawn Feeney-Lear et al. Their club is in flux since Jason Drake (coach) left for Washington State), but they still want to maintain a women's middle-distance to 10K track focus and are still pursuing keeping it together. If you decided to move up, Lorraine Moeller has put together a formidable women's group the past year for 5Ks to thons.
Can't fill you in on the East coast so I'll leave it to the experts. One guy I train with is originally from Pittsburgh so if you need info I can ask him. Ciao.