In DC, MD and VA, I can buy lots of D&G Sodas at Giant Foods. Most of the Giant grocery stores have an international aisle and that's where you will find it. Also, I would assume most larger cities would have an international grocery store and you should be able to find D&G and other Jamaican products.
Even though it's D&G, it still taste very different then the ones you get in Jamaica. I think it has to do where it's bottled.