It may be a little late responding to your message, but I'll send a response anyway. I've only done the Dunn's River Falls. I was rather disappointed in it. I live in Pennsylvania and we have lots of rivers with water falls in the Laurel Mountains. And I expected the falls would be just as impressive as the ones I saw in Hawaii. So my expectations were too high.
I'd recommend the excursion it if you've never seen falls before. The climb can be a little dangerous. They expect you to form a human chain, you depend on someone in front of you to help you up and someone behind/below you not to pull you down. My boyfriend and I ended up breaking off from the group and climbing separately. It was much easier and safer. I wore Keds type shoes for the climb and they were fine. It was fun, but not nearly as impressive as I expected. With not much else to do in Jamaica, it may be your only choice. Of course there's always snorkeling.
As far as the locals, I found them to be very pushy when you walk through the market after climbing the falls. They will actually grab hold of you to try to sell you something. But you shouldn't be carrying anything of value for the excursion anyway. I found out later there is a way to get back to the buses without going through the market. But I don't know how.