We stayed a bit closer to Valley of Fire than this spot, at 36.414344,-114.605350.
It's basically a big pullout along the road but it's fine for an overnight. After we got there two more vans pulled up later in the evening and there was plenty of room for everyone. There is a little dirt road that continues down, and we walked it but wouldn't recommend driving it unless you have a 4x4 and high clearance. The spots down there aren't that great anyway, they're tiny and hilly.

But the whole area has plenty of boondock opportunities so check it out on Google Earth or satellite and proceed at your vehicle's ability. Great place to stay the night before heading into Valley of Fire.

Ok cell reception for both Verizon and att.