I use an evaporative cooler, works well with the dry climate and it is simple enough that I can do any repairs myself (no electronics, just a pump and a fan and switches for them), and is very energy efficient. I've also read about digging pipes that go deep underground to circulate air for cooling. I'd think about getting a heat pump but my main concern is maintenance, have heard from people whose heat pumps broke down and they had some trouble getting them fixed. It's not totally unambiguous that it is the best choice in all circumstances.