You will need to fill at la posa south. It's about 100 yards past mile marker 102 heading south out of Quartzsite on 95, on the left. You will need to pay as you enter, then carry straight on up the gravel road for about a mile. You will see the queue on the right to dump tanks and the dumpster on the left.
Just pass these you will see stand points on either side of the main gravel road.
Once filled, go back out to highway 95 and straight over, your pass will give you access to all LTVA areas, bear right after the booking office then as you get to the 15 mile per hour sign, bear left. Keep on the main gravel road until you see the second 15 mph sign. Just past the sign you will see a worn gravel track going off to the left. We are up there about 200 yards.
Safe travels.
(Be careful as your turn left into La Posa South, the tarmac is badly worn and full of holes)