To answer the question more specifically.... at CTI (our only experience), Red Stripe was found on draft at one or two of the main bars. Red Stripe and Red Stripe Light were in bottles on the island, and also at other bars (at least at times). Guinness and Heineken (both brewed in Jamaica) were in bottles in the Piano bar. Carib and Miller Lite were the two beers available in cans.
Thanks mu77tx. It should be fun trying out the Jamaican Guinness and Heineken and comparing the taste to what we are used to drinking. Our friend is a Guinness Snob so his reaction should be interesting.