Mt Palomar is a great place to go camping. It has forests and trails for hiking and it's National forest land so dogs are welcome.
Science buffs and families are drawn to Observatory Campground for its proximity to the Palomar Observatory, a world-class center of astronomy research operated by the California Institute of Technology. Just two miles from the observatory, the campground provides visitors with a unique learning experience in the great outdoors. The facility offers a variety of amenities for both tent and RV camping. Hiking, biking and picnicking can be found nearby.
The campground sits at an elevation of 4,800 feet in the Palomar Mountains of Southern California. The site is forested with pine and oak trees, though several sites have been cleared to allow campers a wide view of the night sky.
Information on the campground: http://www.fs.usda.gov/recarea/cleveland/recreation/camping-cabins/recarea/?recid=47560&actid=29
I have reserved site 13 for the weekend. There are several trails in the area for hiking or mountain biking or just hanging out and relaxing at the campsite.
Campsites are 15$ a night and can hold 8 people.
It is a 2 mile hike to the Observatory and a few more miles to High Point fire lookout.
From San Diego: 15 North to the 76 turn Right(east) at South Grade Rd(Co Highway6) turn Left and go up the mountain. At the main junction in town turn Left(Candfield Rd) and xontinue to the campground on your RHS