I've tried different tactics, like offering an alternative (this spot is better to skateboard instead of our parking garage), telling of the consequences (people drive too fast, you might end up in the hospital, cars have been damaged, you're leaving trash), actually pointing to the rules (look, it's written here), none of these work. The only thing that actually worked was calling the police. They were happy to help and even offered to patrol every now and then. Get someone of authority and get them to deal with it. — Caroline 1 min ago