Nicollet,
No one in Negril, MoBay, Ochi, Port Antonio, Kingston, or nearly anywhere on the island will take disrespect if you use US$ currency. In fact, with the fluctuations in the JA$, many businesses are more than happy to receive US$. If they think you may be North American, you are very often asked by your cashier, "is this in US$ or JA$?'
Many of the bills on the POS systems at restaurants have multiple currencies listed so you can pay in the currency of your choice. I know this because I helped set many of them up. Obviously they are generally not giving the same rate as a cambio, but they do this not only for convenience but they also have to pay some of their bills in US$.
MegaMart actually has the best exchange rate of nearly any store, or cambio for that matter. That encourages payment in US$.
Although it may seem counter intuitive as most visitors home countries only expect payment in their home currency, Jamaica being a small island nation, much of what is needed to keep the island running is imported - steel, oil, foods, autos, etc. all need to be paid for in US$.
To all,
You are in no way disrespecting any business by paying in US$ or Canadian $ for that matter. Most if not all the businesses have a going rate for these currencies. Euros and British Pounds are a bit harder to exchange on the fly as most businesses have to find out what the going rate for these currencies.