This is the perfect time of year to wander that portion of Anza Borrego. As you figured out, you can drive up to 17 Palms. 5 Palms is not that far of a walk from the next parking area down the trail a bit. All of those washes are fun to explore. Short Wash has some nice stuff, and from there you can either go down Fault Wash (lots of cool rock formations) or over to the short trail that ends at Vista del Malpais. Short Wash to Font's Wash is a nice way to get across that area from east to west.
Keep an eye on the Xcursions Forum, I'll try to set up a trip to that area within the next month or so.
Or, if you're looking for company for a trip out just post up.