US currency is widely accepted in all of those ports. Labadee is RC's private island and the vendors at the craft market will quote everything in US dollars. Actually most of the islands will quote you a price in US currency. Mexican pesos are the official currency in Cozumel and the exchange rate is about 10 pesos to every dollar and the Jamaican Dollar = approximately 62 cents US. I am not sure of the rate between Cayman dollars and US, but everything is quoted in US currency so it really doesn't make any difference.