Drive east of town on the Borrego Salton Seaway, then four miles south on a sand road. A 4WD or AWD vehicle is recommended; sedans have done it in dry conditions but the road sands up after wind.
Get there forty minutes before sunset. The badlands face west, so the last light hits them dead on, and the entire valley below shifts color twice in twenty minutes. Bring a jacket — the temperature drops fast once the sun is gone.