The La Jolla Valley Natural Preserve is located in Point Mugu State Park, in the west end of the Santa Monica Mountains. The La Jolla Valley was acquired by the State of California in 1966 and was established as a Natural Preserve in 1972.
The area can be accessed via the .7 mile, but very steep Chumash Trail in Point Mugu (strenuous but the quickest approach), via the La Jolla Canyon Trail (which has been closed since January 2015 due to mudslides), or in a roundabout way, via the Ray Miller Trail. Or you can hike there from Rancho Sierra Vista in Newbury Park, which would be something in the neighborhood of 6 to 8 miles, depending on route.
In any case, the area is spectacularly beautiful right now in March 2017 after the winter rainstorms. If you are looking for peace and quiet, green hills and wildflowers, this is the place for you right now.