Problem with neighbor: torrents of loud profanity while on cellphone?

I have a neighbor, an elderly woman, who allows her daughter to live in her garage. The daughter has been making the garage residence home to her nephew, a young man about 22 yo, who has a habit of walking up and down the sidewalk in the neighborhood, speaking on his cellphone, basically vomiting out torrents of profanity. At times every other word is f*** or n****** or sh**, you get the picture. This is disturbing to listen to when I'm out in front watering the plants, however he speaks so loudly that I can easily hear him from most anywhere in my house. I've spoken to him half a dozen times asking him not to do this, but he ignores me. I've spoken to his aunt and she says she has asked him not to do this, all to no avail. He and his aunt have about 5 cars they park on the street, all wired with car alarms which go off at the slightest rumble, as well as every morning about 6:30am when he goes to fire up one of the jalopies. He has cussed out two of the other neighbors on the street who tried to talk to him about his behavior. I asked the police about this, they say nothing he's doing is a crime but they suggest that I have no contact with him ("because you don't know what he's capable of")and call them to talk to him. They say they can investigate him and see if there is anything they can follow up on. I don't think the man is a criminal, he just behaves disrespectfully and very inconsiderately. Problem is, in my city there is a lot of crime and not enough police so it can take hours for them to respond to a low-priority call, which this would be, by which time the young man is probably off the phone or gone. What would you do (or not do) about this? Ideas?