Joshua Tree has long been a favorite playground for the L.A. climbing scene. In recent years, it has gained a place on the "A list" of climbers worldwide. The best seasons at Joshua Tree (aka Josh or J-Tree) are fall and spring, although you can expect the occasional snowstorm as late as mid-March. In the autumn months, you beat the desert heat, miss the crowds, and usually can get great campsites without needing reservations.
The rock at Josh resembles Hollywood's idea of a moonscape in the 1950' -- large dinosaur-egg-size rocks strewn across a sandy landscape, punctuated by the occasional Joshua tree. Climbing ranges from very easy to very hard. With more than 3500 routes, there is truly something for everyone -- especially climbers comfortable in the 5.8 to 5.12 range. Classic routes include Double Cross (5.7), Touch'n Go (5.9) and Clean & Jerk (10b). There are lots of bolted routes, although many rely on the now old-fashioned 1/4-inch bolts for protection. Some of the best routes are cracks, so don't forget to bring along your rack. A roll or two of tape is also a nice accessory, since the rock can be rough on tender hands. Since nighttime temperatures in the desert can easily fall to single or sub-zero digits, remember to bring along plenty of warm clothes.
Nomad Ventures (760-366-4684) is the best source of climbing information and supplies. Vertical Adventures (800-514-8785) offers basic rockcraft courses starting at $85. If you're serious about the sport, the four-day courses are a bargain, since consecutive days on the rock are the best way to develop skills and strength.