The trails through the ONF are great for riding around and enjoying the scenery. The trail here from the east is a nice two track with soft sandy parts. As you approach the general GZ vicinity, you'll enter what I call the Pit. What seems to be a local hangout and party scene, the area looks like a large sand pit in teh middle of a desert. The sand here is really soft and 4WD is a must. You could get reasonably close I would think with 2WD and then hoof it in for the rest. A maze of trails leading every which way out of the pit you will find. Unfortunately, the locals seem to enjoy having a great time and discarding their refreshing beverages any which way they choose. A recent clean up has done a lot to help the area, but the fire pit area seems to be the focal point of the local hangout. From the pit, you'll need to make your way to GZ which could be a little whacky as the terrain goes uphill and the trails and open scrub land all seem to connect at various points.
Once at GZ, the cache is easy to find and you are looking for a yellow plastic bison tube 6 feet up a pine tree.