Ronald W. Caspers Regional Park
Ronald C. Caspers Regional Wilderness Park is a public park in Orange County next to Cleveland National Forest.
It's mostly a mixture of coastal sage scrub and chapparal, with some "riparian habitat" -- the mixture of trees and bushes that grow near creeks.
For many years, it didn't allow children because of two mountain lion attacks in 1986, but the restriction was lifted in 1995. As far as I could tell from looking at the court testimony, the first attack was not the parents' fault in any way, but do keep an eye on any kids you bring along; many of the trails wind through fairly heavy brush.
The entrance is on Ortega Highway, about 8 miles inland from San Juan Capistrano, off the Interstate 5.