Great option for J Tree
Although it's technically in the park, you'll need to drive over to one of the main entrances for park access. Still, this is a great option. The horse stalls are on the north end of the camp, and there are a few loops. It's desert camping so bring your own shade and lots of water. The weather was great in October, and there is a short trail on the west end of camp (plus lots of other in the area to explore).
We had an RV so I can't speak to the bathrooms.