Just south of San Clemente, off Basilone road, you continue driving south past the powerplant toward San Onofre State Beach, where there is a campground, along with miles of bluffs, and trails.
I would be hiking down the West Ridge, then making a right on Mathis Canyon. I would then make a left down Coyote Run and explore Wood Canyon, before heading up a trail called Rock it. This would be a 6 mile hike and great for conditioning.