try starting with socalcarculture.com. Run by a H.A.M.B. member. If nothing listed contact him on site and maybe he knows where to check.
there's a decent one on coast hwy just south of carlsbad in encinitas but it doesn't start till april or may, i think it's the 3 thursday of the month. cruising grand in escondido runs from the first week in april through october and is every friday, usually a few hundred cars. there's also a sunday morning breakfast deal by fallbrook just off the 76 by mission road, there might be a few guys out there this time of the year but it will definetly have a bigger turn out over the summer. every saturday? (might be sunday) there's a show where the 5 and 405 split is in the mazda? ford? parking lot, i've only been to it once and it was mostly newer stuff but still sorta neat.