At first I signed on the trip to San Andreas Fault, but later the company told me the temperature would be too high in the fault, and offered me an upgrade to Joshua Tree NP. It was very considerate, the sunset was gorgeous on the Eureka Summit, and the weather was much cooler. All of my family, including two 3-year-old kids, enjoyed the trip very much.
The best part of the tour was our guide Josh. Usually I don't write comments on the internet, but this time I do it for Josh. He was super nice, patient, and knowledgable. We learnt from him the history of the desert cities, animals and plants around the park, geology of the district, as well as other interesting social issue of America. Especially one thing impressed me was he would stop and clean the trash on the roadside in the park. He really loves our planet and his job.
Yes, you can drive to see the park by yourself, but a good guide would make your tour really different. I really wish I could travel together with Josh for the rest of my journey!
Some said the tour was not off-road. In my opinion, it is off-road in the park, for around two hours. I don't think the SUV we rented could make it. Hummer in the wild is indeed an unusual experience.
I agree the price is not cheap, but I think the joy my family got did worth it.