Black Rock is a wonderful national parks campground in Joshua National Park. It's the easiest park to get to so it can get crowded on the weekend. The camp spots have about 15 years between each one. There's a bench but no hook ups. There're water spigets throughout the campground and an RV dumpsite ($5). The store is open from 8am to 4pm. 

Hiking: There are a few hikes that leave from the campground. Take the West Loop Trail to explore the area and hike up to the High View Peak to see the surrounding area. 2-3 hours. 

Cell Service: Roaming (3bars)