I'm planning on only using my credit card at the hotel and duty free.
I did have to call my bank and inform them.
If you have a Bank of America debit card, it works with no extra fee in the Scotia Bank ATMs. (B of A told me they still add a 3% international surcharge, though. There's just no charge for using the ATM.) If I need Jamaican dollars, I'll go there.
I'm also bringing Jamaican and American dollars with me. (small bills)
