Being from Canada, I have gotten to the point where I don't use any USD at all...unless I take ~$50 worth to get me started until I can get to an ATM or cambio (outside of the airport). I have JMD leftover from my last trip so it'll be JMD all the way for my upcoming trip. If quoted USD at restaurants or for excursions, I ask for the price in JMD. Most times you save money using JMD. True or not, I believe that using JMD is better for their economy and that if most people used it, it would benefit Jamaicans in the long run. Sadly though, it seems that USD is becoming more widely used by tourists all the time. As is the situation with imported foods, Jamaican farmers suffer. I say buy local and use local currency whenever possible, it's just the right thing to do.