For MX you have either the El Cajon track, Cachilla up past Escondido, or Elsinore which is about an 1.5 hrs away, depending on where you live. We have a few riding areas within .5 to 1 hr away (Corrall Canyon and McCains Valley). Within about 1.5 hrs is the desert (Ocotillo Wells, Superstition, and Plaster City). Then the Dunes are about 2.5 hrs away. You'll need to go to the dunes at least once. It's a blast. If you're looking for group rides check the So. Cal wrecking crew forum in the reginal area. I plan on hitting the desert in Oct.
I don't even ride yet, but what about the dirt track next to the go cart track out by Palomar mountain. I think it's called Amago or something. Anyone been out there? I'm thinking about getting a dirt bike soon and also need to know where I might ride. Where do you go to ride trails in SD?