Most of the Palomar Canyon road is just "fine" - the usual bumpy dirt track. Below is a random example shot from my dashboard cam. The road goes up the canyon, but avoids the wash itself except for where it has to cross in a few places. These crossings are where the dirt is all washed out, leaving all those soccer ball rocks. The photos I posted earlier are from the longest crossing, where the road stays in the wash for a quarter mile. It's the worst of it. There a few other crossings, but they are more like 100 yards. Overall the 5 miles of canyon road took me 1.5 hours, including what my GPS says was 45 minutes I spent moving rocks at that one spot.
All that above is the "fun" difficult road. The other aspect is the tediously awful roads you need to take to get access to the canyon. These are beaten up from frequent use and racing. Coming south from Highway 2, there are 30 miles of heavily washboarded dirt road up to the Guadalupe Canyon turnoff, followed by 20 miles of soft sand/gravel that has undulations that make any speed unpleasant. The other option is to come east from Highway 3, which only 30 miles from pavement to canyon, half of which is on dry mud and half on that undulated soft sand/gravel.
Here are some photos of what I mean. It's difficult to really see how tedious it is in the photos, but sand/gravel is really soft and undulates such that you can't just speed over it like you can with normal washboard. There are lots of unofficial side tracks where people try to avoid the main road but it's not always possible:
Feel free to message me with any more specific questions about how to get there, as I am purposely keeping the access directions a bit vague here.
-- Geoff