as for tracks (i.e. race tracks) there isnt really anything down in san diego that I have come across except for willow springs
http://www.willowspringsraceway.com/home/home.asp
but if your willing to drive a bit farther there is always
buttonwillow
http://www.buttonwillowraceway.com/
or laguna seca
http://www.laguna-seca.com/
or California Speedway
http://www.californiaspeedway.com/
but most stuff is up near LA that I have found so far
I havent ridden any because their all pricey (willow springs is the cheapest at like 150 but SD House of Motorcycle does Track Days up there a couple of times a summer... Most of these are in the desert so you might have to wait another month or so till it cools down some... the desert makes some realy bad (miserable) track days 115 degree heat is no fun
good luck in your searches..