There is no water on the trail, so due to the length and remoteness, this trail should only be attempted in cool weather (late fall through early spring). Also, this is not a DH ride. Sure, there's plenty of DH but you need to pedal a fair bit too so an AM type bike with big tires would be ideal.
The trail was in good shape and pretty well marked as of 1/1/2014, so for the most part you can follow the other tire tracks for the first 17 miles or so, after which there are several options. If you don't have somebody who is familiar with the trail, riding with a GPS map is highly recommended. At about 13.5 miles, head right up the sandy wash for about 3 miles (yes it will suck). Turn left on Dunn Road, and take that for about 3/4 of a mile, then stop at Mike's Desert Oasis and try to find some shade under the bulldozer and eat some snacks. From there, take the singletrack up the hill (to the west) to ride Hahn Buena Vista Trail. After that we were feeling pretty beat, so we took Dunn Road back to Cathedral City rather than riding the Goat Trails.