HOW TO GET THERE: From San Diego, travel north on I-15 and exit at Highway 76, traveling east toward Pala Reservation and Casino. Turn left onto South Grade Road (S6) and follow this winding road to the Palomar Crest. Make the next left onto Canfield Road and then another immediate left onto State Park Road. Follow State Park to the entrance and pay the $8 day-use fee (at time of writing). Just past the entrance, turn right onto Doane Valley Road and follow it to the parking lot at Doane Pond. The trailhead is on the southwest corner of the lot, closest to the pond and the restrooms.
Doane Valley Loop Trail is a 2.7 mile lightly trafficked loop that is good for all skill levels. No dogs allowed.
Personal Experience: I was thinking I maybe made a bad decision convincing my friends to come up here during a scattered rainstorm. The drive was THICK with fog which, although eerie and beautiful, is really scary to drive in! Once we had parked and were headed to the trail, I fell in a waist-deep sinkhole! I was soaking wet and hit my knee on concrete which really hurt. What a way to start a hike!
After those scares and embarrassments, the real beauty began. There was drizzle most of our hike but the fog made this possibly the most surreal hike I've ever been on. It was SO beautiful. Palomar Mountain is gorgeous any time of the year but when you visit in the winter when it's thick with fog, oh man, it is a brand new experience!