i.e., the Cahuilla people in the Coachella Valley of California, or the Pueblo people of New Mexico?
Having traveled throughout the Southwest, from the Colorado Desert to White Sands, it's incredible to me that anyone could sustain themselves in such climates without modern technology given the lack of obvious sources of water or nutrition.
Keep in mind that the landscape you see today may not have been the landscape that existed in the past at the time of occupation. I'm not suggesting that deserts were once lush areas of vegetation, but they may have been wet enough or had enough year round rivers to sustained animals for hunting and plants for gathering or even agriculture. Case in point would be the Bajio region in Mexico. During the Epi-Classic the area experienced a prolonged drought that may have caused the Chichimec migrations.