We were in George Town a few weeks back on Carnival Vista. Margaritaville is indeed closed. We walked right by it and then realized it wasn't there. The sign is gone an the entire building (where some other shops were) seemed closed.
The Margaritaville in Falmouth, Jamaica was open and we went there on the way back to the ship - just before the skies opened up. It was a nice 2-drink rain storm in the afternoon. Not a bad place to be stranded by the rain. 😁