This is a day trip, with two separate trails. Less than 2 hours from San Clemente to/from each trail, and about 1 hour between them.
Part A. Palomar Divide Road + Oak Grove Road + High Point Truck Trail. We start off hwy 79, north of Warner Springs. The first part is very easy, with some paved sections. There is a fire lookout tower at High Point that looks down toward the Palomar Observatory. Gates are closed between the east and west sides of Palomar mountain, so we stay on the east side, and continue north. Going down Oak Grove Road and High Point Truck Trail is a lot more fun than the drive up. We go past the 15th hole before getting back on pavement.
Part B. Santa Rose Truck Trail. This takes us past Santa Rosa Peak, which we will make a detour to visit. (Note : This would be a fantastic place to camp and stargaze). We then continue to Toro Peak. Great views to the Salton Sea, and Anza Borrego. We come back out the way we went in.
Links from Gaia. They might work
Rendezvous @ San Clemente Carl's Jr (South)
Meet at 7 AM at Carl's Jr. This is day trip. Bring a lunch. The trail begins near Warner Springs.