I get it that high because I just withdraw Jamaican cash from a Scotia bank with my Ally Bank Debit card (I don't go to an exchange counter). I only bring a few hundred cash US when I come down (mainly to pay my car service) and just use the Jamaican cash that I withdraw from the Scotia Bank. Ally bank only charges me a %1 fee to use their debit card internationally, which is why I get a good rate. So my driver from the airport takes me to a Scotia ATM, I'll pull out $30,000JM per transaction (which is only about $230 US deducted from my checking account) usually pulling out a 2nd transaction of $30,000JM to stay under the US daily ATM limit of $500 (and walking away with $60,000JM). Depending on how much I spend during the week, I'll go back to a Scotia bank later in the week for 1 or 2 more $30,000JM transactions to have enough money for my 10 day stay.
SO after saying all that, call your bank and ask 2 things. 1) Do they allow you to use your Debit card in Jamaica? 2) What percentage do they charge for an international transaction with your ATM card? If they they allow you to use the debit card in Jamaica and charge 3% or less in transaction fees, you'll be saving money doing it that way vs going to a cambio. Just make sure you notify your bank before your trip of the dates you'll be using your debit card in Jamaica.
I hope this helps...
BTW, ALLY Bank is an online bank. You can sign up with them for free and then transfer your travel money to your Ally checking account electronically before your trip to get the same exact deal that I get.