Scaddam Wash is a nice spot to camp while transiting to California or Arizona. It's located along the freeway so you will hear traffic noise but have good cell phone reception. Beware that the road leading into the wash is rough and not maintained. Most people now just drive on the side of the road which provides a smoother ride. 

There's a sign at the entrance that list a few of the rules of the area. There's a time limit on how many days you can stay; I think its 14 but not sure. 

In Jan-March there are plenty of RV and Van gatherings in Quartzside. The closer to the freeway you are the more people you will encounter camping. The further you are the less people. Choose what's best for you.

Cell Service: Great