This was a Critical Mass event, which is why the bicyclists are taking up all of the street as a way to reclaim the streets and protest the lack of safety for riders under usual conditions. It’s not legal, but protests are never useful if they’re fully legal now, are they.
This looks like Miami. If it is… critical mass usually has a police force in the loop they do usually to stop people driving right through the crowd. The loop is posted online about a week before and there is always police presence
Probably LA? Looks similar but police less likely to beat the shit out of white people on bicycles