The popular single track trails are way too crowded right now. Please share these links or contribute more links if you agree.
Here are a couple less-crowded access points to the Palm Canyon Wash:
https://goo.gl/maps/yq2E4fbuWSQi7ijd9
https://goo.gl/maps/hocqeJ4msh6LChGB6
Dunn Road (dirt), a 4000-foot climb:
https://goo.gl/maps/kcKGnmne5Xb6ZgU6A
Tramway Road (paved), a 2000-foot climb:
https://goo.gl/maps/6HBUPbTvyrHc29KN7
Demuth Park bike path (paved with sandy shoulder):
https://goo.gl/maps/hBXAggo4WY5XXEE87
Bogert Trailhead:
https://goo.gl/maps/iaDbCxiE4kJd4vvTA
Rimrock is a dirt road but is very crowded. Top of La Quinta Cove is probably similar right now.
The worst: Bump n' Grind, Homestead, Museum, Araby. Even Garstin and Lykken are crowded. North North Lykken is single track but not super popular.
I have never done the trails near the national monument visitor center off Hwy 74. Art Smith is somewhat popular single track. Hoppalong Cassidy is not frequently used, but the major access points are. The Palm Desert wash is good for social distancing.