Dozens of community artists wielding paint brushes and spray cans celebrated street art at the 18th Annual Urban Youth Arts Festival on Saturday. The festival, organized by Precita Eyes, invited artists of all ages to express themselves on 1,000 square feet of portable wall space at Precita Park on Precita Avenue near Folsom Street. Like street art itself, the canvases are ephemeral—they’re recycled from year to year.