Use Quail Trail to get from Irvine to Laguna Coast Wilderness Park. It starts out semi-paved but quickly turns into a doubletrack/dirt road. It's extremely steep at the beginning of the dirt road but levels out after you are on top of the "hill." Quail Trail eventually turns into a singletrack with a few easy switchbacks and then descends to West Canyon where it turns into Serrano Ridge.
This is a neighborhood trail used as a connector to longer trails at Laguna Coast Wilderness Park and Crystal Cove. Parking is free at Quail Hill Trailhead. The trail starts across the street on the side of the athletic field. Look for the steep grade a quarter mile in and veer right when the trail splits.