Vekol Exit 144 free BLM dispersed
This is free dispersed camping on the BLM Sonoran National Monument. At Interstate 8, Exit 144 go south. BLM starts in about .6 mile. Note that the gravel road then will pass thru some pvt land that the Dyrt does not show, before the BLM again at the road fork to the Vekol Ranch (2.1 miles in from hwy). See attached screenshot from the BLM monument map. Lots of sites scattered along the main graded gravel road. There is an info kiosk at junction of road going to the Vekol Ranch. Most of the campers seem to be in this area to avoid interstate truck noise. Excellent cell signal on all carriers. No water, marked sites, tables, fire rings or trash dumpsters. Nearest services are in Sanfield (poor), Maricopa (best) or Gila Bend (fuel, RV stuff) so come prepared. Maricopa has a Fry's Market and gas. Sanfield has a Family Dollar and Circle K gas. Gila Bend has most services but not a major food market. Not much Sonoran cactus vegetation by the kiosk sign in in this area, no cholla and very few Saguaros, area is just a wide flat creosote palo verde sandy plain.
Update: if you go another mile or two south (uphill) on the main road you can camp at the #8007b and #8007c road spurs and #8045 spur. More Sonoran vegetation there and very scenic...lots of Saguaro cactus to camp with on flat open desert pavement. Farther away from the hwy noise is a plus!
If you are concerned about potential safety issues from illegal smuggling warnings, then staying down close to BLMat the .6 mile mark is likely best.