Since you are on the Conquest, you will be going to Montego Bay. I think there is only 1 drink that is $20, the drink I had was over $7 and didn't even come with the glass.
If you want a great place to go, try Sunset Beach Resort, it's all inclusive, 5 minutes from the ship and only costs $20 per person. Includes all you can eat, drink, 3 beaches, 2 pools, swim up bar, activities, kayaking, snorkeling, etc. We did this and loved it. Probably would skip shopping and everything else next time and just hang out at the resort all day