Hi Oscar,
Summer time in Arizona is notoriously hot and dry, with monsoons occurring in late August or early September.
October til middle of May is the high
season in Arizona, therefore the last two weeks of May would probably be the best time in terms of hotel prices, attractions, etc. Also, the weather in late May tends to be cooler and a little be more pleasant.
Some attractions that you
must-see are as follows:
* The Grand Canyon
* The reservation lands of the Navajo Nation
* The Canyon de Chelly National Monument
* The Casa Grande Ruins National Monument
* The Besh-Ba Gowah Archaeological Park.
Hope this helps
VacationBuddy