There are plenty of climbing routes in and around Anaheim Hills, Yorba Linda, Orange Hills, Santiago Canyon. For a quick jaunt from SART, try heading towards most any of the streets surounding the north end of Newport BL. Or from SART/Imperial Hwy, head east on Imperial and you'll be in 10-12% territory in no time. Whitecarbondude has some routes for Yorba Linda/Anaheim Hills.