The local beer on Puerto Rico is Medallah, a pretty good beer with a nice refreshing taste.
"El Presidente Cerveza", from the Dominican Republic, is a popular import beer too, as well as Corona and some American brands.
However, the most popular non-local beer around here in my opinion -- and I am writing this with some pride -- is Heineken from Amsterdam. Even though it's not the best beer that Holland is offering the world, it is nice to be able to drink a familiar taste everywhere you go.
