I rode along the north ridge of Palomar today, up High Point Truck Trail from the 79/371 intersection near Aguanga and down Palomar Divide Rd., exiting 2 miles south of Sunshine Summit/Holcomb Village.
Also spoke with a ranger at the Oak Grove station on hwy 79 who mentioned Oak Grove Truck Trail is gated as it crosses private land.
There's another route to the top, Halfway Truck Trail, which intersects hwy 79 at Sunshine Summit.
This is gated seasonally but the ranger believed it is currently open. I didn't check.
As BajaRider650 mentioned, there's a gate near the firewatch tower that effectively seperates Palomar's north and south sides. There's also a gate at the bottom of the spur road to the tower so I wasn't able to ride up to its base at High Point.
The roads are in pretty good shape and certainly big bike friendly (BBF?) as I managed tolerably even on my R80ST striped street pig (SSP).
I saw two trucks on my way up and four parked at the Barker Valley trailhead.
A few miles at the southern end of Palomar Divide Rd. are primitively paved.
High Point Truck Trail
Palomar Observatory from the gate
just a short walk to the tower
Barker Valley trailhead
fine views all day long