I would not go shooting in the desert near Casa Grande or anywhere else south of Florence. The area is smuggler's corridor. Posted by the BLM and Border Patrol that entry into the area is dangerous. During parts of the year, the areas near Arizona City and south are posted no entry at all, due to a temporary rise in smuggler activity.
The USFS areas north of Florence have just re-opened to shooters after having been closed for the extreme fire hazard areas.
I'd suggest, if you're in Florence, a call to Mr Babeau's office to ask where it's legal and safe. I'm guessing that NORTH of the Gila river and EAST of SR 79 is a good spot to look. There's houses up near Cottonwood Canyon and the hikers are up closer to Superior and north of US 60. But most of the cattle and farming is on the WEST side of 79. Unfortunately, nearly any desert shooting spots you'll be able to find will likely be overrun and trashed by disrespectful and drunk ATV riders.
Sgt Lumpy