Telegraph Pass Trail is Yuma's classic close-to-town workout, climbing into the Gila Mountains east of the city. The route is short by mountain standards but steep enough to feel earned, and the view opens across the desert, irrigated valley, and distant Colorado River country.
Treat it as a desert hike, not an urban stroll. Start early, carry water, and avoid the exposed climb in serious heat. Winter and the cooler edges of spring are the best times; in summer, sunrise is the only sensible window.