The BLM lands a couple miles due S of Ajo are quite suitable for dispersed camping most of the time; access is via the Scenic Loop Rd either from the SW or SE outskirts of Ajo (skirting the huge mine tailings). Alamo CG within OPCNM isn't dispersed per se, but a bit more secluded than the main Twin Peaks CG. Also some dispersed options in the area immediately adjacent to Why. However you do it, enjoy mightily.
Rico.