If you are going to take one hike in Tucson, Tested Travel recommends Sabino Canyon!
Located in the Coronado National Forest, the Sabino Canyon Recreation Area is a wonderful and accessible visit to the desert foothills and gorges.
For those who prefer to ride, a free tram provides access to Sabino and Bear Canyons. You can get off and on the tram allowing you to marvel at the flora and fauna of the canyons and take a dip in the cool waters of Sabino Creek. The visitor center provides a great overview of the area and has trail maps. In Sabino Canyon you can hike, bike, picnic, swim, and just enjoy the great outdoors!
Speaking of trails, there are miles of hiking trails that wander throughout the area and lead deeper into the Santa Catalina backcountry. It is lovely country, but be sure to always have water and watch for storms that can create flash floods.
Read more about the site here.