The Southern Arizona PCA group is pretty active and sponsor a fair number of DE's and Autocrosses. They use Inde as well as the Musselman Honda track which is a lot closer among others. They also have social activites, car shows, concours, tours, etc.
PCA Southern Arizona Region - It's not just the cars, it's the people.
Things slow down a bit during the summer due to the heat, but pick up in the fall.