Stay in areas where there are plenty of other tourists. I found the peolpe to be extremely friendly and very respectful, but I did not test the back alleys.
If you do the Dunn's River Falls, (Ocho Rios) try to find a time when it won't be crowded. It is very beautiful, but the crowds can take away from that.
Even though they have a reputation for pot, and I know it was there, I was only offered to buy it once, and that was at the airport.
Also, when I was there, (13 yrs ago) you more than doubled your money when exchanging on the black market. This is illegal down there, so I had a friend exchane some for me when he did. I was affraid I'd get locked up forever.
Have fun.
J