One of the reasons we stay on the cliffs is because there are very few hustlers. For the most part they are not welcome at the hotels. While on the beach I have used a couple of lines that worked (and both are true). When offered weed I tell them I am a Christian and don't smoke. I have yet to have them offer a second time. A little funnier: when constantly asked for a massage I told them my wife gives me a message, and she does it topless. They couldn't compete with that one either. I know neither instance is not the same as you experienced and am sorry that a few bad apples ruined your time in Negril.
Regards,
Bob