I'd love to help with a track in SoCounty!! There are no facilities down here--and I TOO believe you would be able to pull as far south as SD for a nice indoor facility. If your really serious--I don't think you could go wrong with a facility like Westcoast in La Mirada. Danny has done his homework--and the onroad asphalt works really well.
The dirt track is made out of clay--instead of just dirt--and that allows water to be held really well with nearly NO dust kicked up to ruin the onroad track.
The curbs on the onroad track work VERY well also--so you should note that as well. I'm sure you could get the same asphalt company to lay your surface down-- then it's up to stocking the hobby shop side of the business with enough parts to keep the regulars in tires /batteries and car parts.
FWIW
TIm