It depends on what you like to photograph. But, as a Tucson resident whose passion is wildlife photography, let me add my two cents.
1. Arizona Sonoran Desert Museum. The grounds are a large desert preserve and there is plenty of wildlife, both on exhibit and roaming free. The highlight of the day (until April 19) is Raptor Free Flight at 10 a.m. and 2 p.m. The two shows are different and they afford the opportunity to get fantastic closeups of birds of prey in flight and perched. A must!
2. Sabino Canyon. A great place to photograph lizards and, possibly, a snake or two. It is a well known location for seeing Gila Monsters in the wild this time of year. No guarantees, but your chances there are better than in most places. The area around Sabino Dam is a hot spot for wildlife watching.
3. Sweetwater Wetlands. This is a man-made marsh on Tucson's west side. Take Interstate 10 to the Ruthrauf Road exit, then take the west frontage road south for one mile, turn right on Sweetwater drive, go about 200 yards and it's on your left. The ponds and swamps there attract lots of birds, including some fairly exotic species like Soras.
4. Silverbell Lake at Christopher Columbus Park. A great place for photographing Great Blue Herons. Also take the Ruthrauf Road exit on I-10, head west one mile, turn left on Silverbell, go south about 1/2 mile and it will be on your left.