For a few hours Sunday, the labored hiss of city buses and the whir of passing cars went silent on a half-dozen blocks in San Francisco’s Tenderloin. In its place came the screech of skateboards, the tick of bicycle wheels, and the throbbing bass of synthesized pop tunes from a DJ booth. [...] sidewalks normally occupied by homeless panhandlers instead were overrun with children in playclothes and couples holding hands. The Tenderloin, with its reputation for grime and crime, has one of the highest percentages of school-age children in the city. Sunday Streets brings family-focused activities and man-made open space to an often-suffocating concrete neighborhood, organizers said. “Everybody is talking with each other, kids are playing carefree, visitors are exploring,” said San Francisco Board of Education member Matt Haney. Near Civic Center Plaza, workers erected a rock-climbing wall and a pop-up skate park. Parents pushed toddlers with bedhead in strollers, and staff from the nearby Main Library carted out books to be displayed on folding tables. At the Golden Gate Avenue health hub, there were free blood-pressure screenings, a protected bike lane demonstration and tours of a clean Muni bus — a rarity in and of itself. [...] at the temporary picnic grounds set up on Larkin Street, families on blankets ate Vietnamese food and listened to bluegrass music. Katie Soto, 40, watched her young children play with jump ropes and bubbles and talk to police officers and street sweepers. Other children flitted nearby, or used chalk to draw looping clouds and suns and basketballs and baseball bats on the cement sidewalks.