All Cars, all paved. On Montezuma Valley Road, 1 mile south of the Visitor Center, park in the parking area.
This is an one way trip from Jasper Trail to Borrego Springs (3.5 Hours), with a car shuttle at the end.
Or as we did it, one day from Borrego Springs and return (stopped at "stop" (4.25 hours round trip)
Another day from Jasper Trail to "stop" and return (3.50 Hours).
The Jasper part is by far the easier part, and the part with most of the views.
If you have to choose take this part.
The upper part will be a lot cooler (10F).
Accessible at both ends with a regular car. (Montezuma highway).