My son and I tent camped on the Ft. Bliss range’s south training zones circa 2014 at a place called Kerby Tank (see google maps) on the east edge of the range. It was a great adventure. Very empty and quiet with a great view of distant, northeast El Paso and the Franklin Mountains at sunset. It was free but we needed two sets of permissions. First you need an annual range permit at the Buffalo Soldiers Gate. Then you need to call Range Control and ask to camp. Watch out for UXO (unexploded ordnance)!