Well outside of how it effects the local economy, after much thought, I've found that it's most cost effective to just spend US currency because of the 'double whammy' of losing out on the exchange rate when you buy the Jamaican $$$'s and then losing again when you trade back the extra Jamaican $$$'s when you leave. The key is bringing half, if not most of your money in small change ($1's & $5's). Small change is key because when dealing with a small bar/food bill or 'beach vendor' you always take a beating if they owe change (it's very rare they give you US $$$ back in change). Plus, on the occasion you have larger US bills and they give you Jamaican change back, at least the locals are getting the difference and not some 'godless bank'! LOL... Anyways... just my 2 cents...
