Once summer is over, you can explore Joshua Tree and the Mojave Preserve more if you are into hiking. I really came to appreciate JT. Military get free passes to the national parks.
I took lots of weekend trips to San Diego, LA, Vegas... always found cheap hotels on priceline/etc.
Big Bear is beautiful, especially this time of year its cooler up there and a quick drive. Same with the tram down in Palm Springs, both are great in the winter as well to get some time in with the snow.
I took some random classes at Copper Mountain College to get out and interact with other people, find out about things to do in the area, etc. If you are military, classes are discounted.
If you take the time, you'll find plenty to do. Even after 3 years, I kept finding more places to explore and people to meet in the Morongo Basin. I really used my time up there to work on a few personal goals, once I saw my 3yrs in 29P as an opportunity it became a long retreat :)