I do sympathise with you. We had exactly the same problem, and couldn't escape from the night-time noise - again, youths who had been chucked out of school, nothing to do, would sleep till noon and then party in the street all night, drive their noisy motos up and down and rev them outside the house, etc. I got so tired we eventually quit and came back to our (quiet) house in England. Over a period of several months made numerous representations to the mayor and other leading lights, and some efforts were made to get them to behave in a more considerate way, but the mayor said he couldn't evict them. It was a private let, rent presumably paid by social services. The main offender seems to have moved on now, but occasionally shows up, so we're not out of the woods yet. Like you I am desperately sorry for the older folk - they're too scared to complain, but they tell us that their lives are being made hell by these people. Good luck.