The 2 closest mines to you that I can spot are coal mines, The Black Star and the Santiago mine The Old Dominion mine is possibly a gold mine coords ar N33.3962 W117.26.22 The Good Hope mine is a gold mine coords are N33.44.30 W117.17.09 its just north of hiway 74 about half way between I15 and I215 ;D
I lived in Jeffrey Canyon near Silverado Canyon and always understood the mines in the area to be silver mines. The Orange County Mining Co. restuarant in the city of Orange is also on the location of a old silver mine. I'm not aware of good area to prospect for gold in OC. most of the local gold mines are in the desert and east San Diego county.
Since my first post I recieved a copy of California Gold Districts. It lists one mine in Trabuco canyon last mined in the 30's. mainly producing tin, copper and zinc with small amounts of gold. The most productive canyons were Trabuco, Santiago and Silverado. Who knows, it might be worth doing a little looking. It lists the Good Hope and other mines farther south in Riverside county.