Hills of the Moon Wash is in the Badlands in Anza-Borrego Desert State Park. Access it from Hwy 78 via the Borrego Mounatin Wash Rd (5.5 miles) and cross the San Felipe Wash. The road up this wash starts out fairly easy but gets more difficult as it becomes more narrow and twisty. The wash is 3 miles one way.
A high-clearance vehicle is definitely required and 4WD is highly recommended.