Small bills in either JA or US can sometimes be hard to come by. I know I lose a bit to the exchange buying $US before I leave Canada, but the small US bills come in really handy, especially $1s and $5s and to a lesser extent the $10s. If I remember, I went to my branch and got 30-1s, 20-5s and 15-10s before we left.

$5 a day to housekeeping (and at the right bar a pair of Redstripe), $10 for cab rides between the beach and cliffs (not trying to start a route taxi debate, that is what worked for us), $1s for tipping helpful folks along the way. We were there for a week and that seemed just about right - it all got spent.

Still being relatively new to JA$$ myself, I also found it comforting to have a more familiar currency for the first few days while we got used to JA currency.

I agree with Sunray, it doesn't make much sense to convert to CDN to US and then to JA. One of the advantages of being with a Canadian bank in Negril is how easy it is to take money out at the Scotia Bank. If you not a Scotia customer, be aware that you will be charged a fee for each transaction (RBC charged me $3.50). Plan to take out more less often, if possible. Also, make sure you know how much in JA you want when you go - it was a bit of a gut check asking the machine for $50,000.