This little spot is two blocks west of 6th Avenue, just off the El Paso & Southern Greenway (a bike/pedestrian path that's under construction; click there for the plan), in the city of South Tucson. As this Google Street View photo shows, there are a couple of benches:
There's a closeup of the mural in tomorrow's entry, La Capilla Neighborhood Garden, on the Tucson Murals Project blog. (The link won't work until tomorrow, February 2.)
LOCATION: Three blocks west of 6th Avenue on 34th Street
PARKING: Street parking
HOURS: Irregular. The gate was locked both times I stopped by.