You will almost never get a good exchange rate at home. You are better off exchanging a few bucks at the Mobay airport if you need cash for the ride, then exchange the rest at a cambio in town. Better yet, just stop at an ATM or cambio in Mobay before you get on the back roads. We like to stop at Jerky's for jerk chicken and Red Stripes, since there is a Scotia Bank ATM right next door.