Search TMC for the thread about the two guys in Texas who drove their S to Panama. Pretty sure that's the record for farthest south when starting in the US!
Another great place. Been to Cuba twice - both on sponsored legit trips. I have to admit in Dec 2015 Cuba did not have as much charm as earlier when it was still less developed. Get there ASAP to experience the charm.
I've seen a couple of older (nosecone) model S in Trinidad and Tobago in the Caribbean. They were right hand drive per local regulations, so likely imported from Japan or the UK.