This route works best if you stash a car at the Palm Canyon Campground or the Visitors Center. As of Feb2005 there are no gates or parking time limits for the Visitor Center parking lot. Once you arrange shuttle service proceed as follows:
From the town of Borrego Springs, find Christmas Circle (this is the roundabout in the center of town on Palm Canyon Drive.) Head north on Borrego Springs Rd (this is called Santa Rosa Drive on the USGS maps) for about 3.5 miles. The road will dogleg sharply to the east. Look for a dirt road that heads directly west, up into the drainage to the north of Indianhead. Drive as far west as your car will comfortably tolerate. (Note there are a few decent camping spots here - reasonable bivy spot if you want to get an early start.)
This will be your blast off point.
From the aforementioned campspot, proceed up canyon until you arrive at a large subsidiary drainage emanating from the north side of Indianhead. You should get a lineup of about 13degMN if you line up w/ the peak.
No real route or use trail exists; kind of a bushwhack without the bushes. We tended to stay on the ridges as much as possible; at one point we did get into a minor drainage to the west of the large ridge. Basically just follow your nose and keep climbing up.
After you top out, continue south to and down the south slopes to eventually run into Palm Canyon and head down canyon to meet up with your shuttle. Keep an eye out along the way down for the bighorn. When I did this loop in '03 we found the remains of a borrego in the southside drainage which we pretty much followed most of the way down (the drainage, not the carcass.)
no technical gear required but bring plenty of water as none is available until you get to Palm Canyon (filter this if you want to drink it.) Lots of ankle-breaker size talus blocks so sturdy boots and trekking poles will make life easier. A headlight will be most helpful if you get caught out late.