This was my sole purpose of going onto the island during our last cruise and we bought tons for ourselves as well as to bring home for people.
My personal brand recommendation, and the one we brought 12 lbs of to bring home, is the JaBlum brand. They have two types (
amazon will help with this) and the pricing is consistent. It's also very easy to find because JaBlum has a company store directly inside the Falmouth port area and that is where I would recommend you find it. They also have the coffee drinks for sale so you can order a cup before you decided to drop the serious $$ on the coffee.
Ironically this is NOT where I sourced mine. I got mine at one of the 3rd party retailers, but I was very specific about finding the Jablum brand because it's only one of three officially certified as true Jamaican Blue coffee and double and triple checked the merchandise.
I also bargained. HARD. The poor shop lady was flummoxed by me and my mother (we're both Chinese-American) when we started yapping away frantically in Mandarin. Having said that, OUR PRICE WASN'T ANY BETTER THAN THE OFFICIAL STORE. I think maybe... $10 difference? When you're spending so many hundreds on coffee, it really wasn't a difference to consider.
So really, I recommend making yourself life easy and just buying directly from the JaBlum store.
As for the coffee itself? I love it and drank 4 pounds slowly on my own, one drip pour cup at a time over the last 6 months. I still have a a few cups of beans left and wondering how long it's going to take for me to break down and buy more. Having said that, my DH did NOT like the coffee as much. He prefers a dark roast and being European, likes a really thick, gritty coffee that JaBlum really isn't meant for. It's more of a medium with a really clear and clean taste. No problem for me though since that meant I could steal his portion without any guilt.