i think the best thing to do is carry a smallish chain with a pad lock on the end in your bag, that was if your in deep trouble you can whip it out and start waving it around in the air.... this alone will proberbly make them run, if not, hit them and ride of quickly..
oh yea and don't ride in that area again, LOL..
if the police ask you about it, just tell them that you need a good chain because they don't do anything about it :)"
will :)