Near Los Angeles / San Diego
Climbing is very popular in the Park. Once considered a training ground for climbers looking to tackle larger challenges in Yosemite (and around the world), Joshua Tree is now a climbing destination in its own right.
Over 3000 Climbing Routes in the Park
But, you know, that 3000 estimate is probably low. Those are just the named routes, but there is climbing everywhere you look.
The Mountain Project maintains a comprehensive map of climbs in the park.
Take a Climbing Workshop
If you've always wanted to try out climbing, then hook up with one of the many companies who will help you get started. These companies have the right equipment, they know the best spots (for your experience level) and they know the park. Start with them first. People get hurt in the park all of the time, so it is best to start out with an expert guide.