To reach East Green Mountain from Christmas Valley, take Millican Road north from Christmas Valley HWY. Cut over to Crack in the Ground Rd or alternatively take Crack in the Ground Road from Christmas Valley HWY. Crack in the Ground road is not paved, but fine for passenger vehicles.
I recommend stopping at Crack in the Ground Road for some Geo-Tourism. It is a short ~1mi out and back hike. Crack in the Ground is as the name describes and is a very cool fissure in the basalt.
To reach East Green Mountain (GPX), continue north on the well maintained gravel road (Lava Craters Rd). Turn west onto Green Mountain Rd. Stay on the gravel road and make a right at 43.38346, -120.72471. There is a sign pointing to a viewpoint. At the top is a large cinder turn around. This is actually in the Activation Zone, so you could operate from here. On the drive in you'll see a very robust looking fire lookout tower. This is on the main Green Mountain (appears to also be in the AZ).
I chose to do a short hike to the true summit. There are some moto tracks that sort of cut a trail in that direction. On the true summit there are plenty of trees for shade and to support antennas.
The HF conditions were good and I had pileups across the bands, plus some S2S. I did get one 2 meter S2S contact with WJ7V on Hamaker (W7O/CE-051).
If you are interested in doing some additional Geo-tourism, there is a basalt cave to the northwest of East Green Mountain (GPX). Follow Green Mountain road north and then take a left and another left on the dirt road. Take a right and park in the shade of a tree. The cave is refered to as "Pothole Ice Cave" on some maps. It is in the basalt to the left of the road. Approx. coordinates: 43.40894, -120.74484.