The currency is the Jamaican dollar (JD) which currently has an exchange rate of 61 Jamaican dollars to 1 US dollar. The best places to exchange money are banks; cambios and hotels/resorts do not give the most for your dollar.  US dollars are widely accepted however most establishments do not have enough US currency to give it back to you when you pay for goods or services...expect Jamaican dollars.

US Dollars are widely accepted in Jamaica, and seem to be preferred.  Just don't expect any small change back.

It is rare to have any problems paying for anything in US dollars, and any business has a calculator handy to do the conversion.  Any change due back to you must legally be given in Jamaican currency.  Sometimes, you can press that your change be given back to you in US currency, particularly if you've just seen the merchant receive USD.  This is however, at the merchant's discretion.

The official exchange rate in December, 2005 was about J65 = US$1. 60 to 1 seems to be the official "unofficial" exchange rate most everywhere else at the time, used everywhere from grocery stores to jerk stands.  You can change money at any "cambio", look for the signs or ask someone.  You can also change money at the grocery store.  The rate can be slightly different

At times a vendor can make a  "mistake" doing the mental conversion calculation whether by accident or intentional.  If it's important to you, to not feel taken advantage of, always do the math yourself, state the US price, and gently insist when you are correct.  Tipping should be optional and at the purchasers discretion. 

Cash and other negotiable instruments in amounts greater than US$10,000 brought into or out of the country must be declared at Customs.

There are ATM's at banks and many gas stations.  Be aware of your surroundings and try to avoid out of the way ATM's at night - just as in the US.  Many ATM's require you to insert your card to open the door to the ATM room - assuring your privacy and security during your transaction.  There is a USD ATM machine in the departure terminal at the Montego Bay airport.

Be aware of your financial institutions fee structure for foreign and foreign denominated withdrawals.