we had the same prob in my old house got feed up off trying to reason with them every sat night they used to come up the road pi##ed up kick every wing mirror off the cars parked up out side i got feed up calling the fuss they wernt to bothered
so one sat i waited saw what they were doing now this was a group off about 8-9 15-17 year old's pi##ed up on cider or what ever anyway i went out had a chat/shouting match smacked the biggest one a good few times they were like scared sheep scatered my car or property were never touched again now i do not recomened this as i am a karate insrtuctor but it worked for me and my neighbour's i have sinced moved and it's started again where i used to live good luck mate i feel for you