In Orange County Crystal Cove State Park has great hiking trails along the ocean. If you go early in the morning you will find the guard shack unmanned and therefore free parking.
In Palos Verdes there are extensive hiking trails.My favorite trail is by the Trump National Golf Course. Keep a lookout for migrating whales.
I haven't been to it, but the newly opened (last weekend) Terranea Resort in PV is also supposed to have public access hiking trails. Their web site even has a map of the hiking trails in the area.
