DLyteful,
I'm a Jamaican now living in Canada, and I make the trip home at least once a year so here's my two cents.
Stick with the CC and cash. So far everyone's advice is good re: taking lots of singles. At the airport it should never cost more than $5 to tip baggage handlers. Before you leave the airport, get yourself some J$, it will always save you money in the end. The Bureau de Change is located in the Departure Lounge, Immigration Hall and Ground Transportation Hall. Their tel876) 979-2673. It's also best to carry J$ to the craft markets and tourist attractions, and keep it separate from your US$. If you feel like venturing outside the hotels to exchange money, the best place to go is Grace Kennedy Remittance/FX Trader. They usually have the best deal. If you go to the Bank, Jamaica National offers one of the best rates. Otherwise, if you use US$, just have an idea of the exchange rate in the back of your mind as reference.
If you've got anything else you want to know, just ask. I'd be more than happy to give you info.
Jamie.