Heading to Puerto Rico for vacation next month. First time.
Advice please!
Bring back the warm weather… 
Ha ha 
I have no idea if this is correct or not because I have actually never visited PR however my father in law is a native and was stationed there when they had a naval base. My mother in law tells me the diet is very starch heavy and she cannot find any healthy food or skim milk. That could just be her visiting relatives though. Maybe if you are at a resort there will be more options?
Are you staying in a resort? They might have nutrition info? Maybe try searching for restaurants and looking into the food options before you go. I googled Puerto Rico Restaurants and a lot came up, just search around the area you are staying. Another option would be to try to stick with generic foods that you know are low carb, though this may not be fun.