From what I gathered here and from trying to do the search on the JW site, you must log in as an elder or servant to find a Kingdom Hall in Cuba. I don't know that you would find it even then.
Catholicism is the predominate belief, Santeria has survived but is mostly blended with Catholicism. Protestants and a few others are there. Jehovah's Witnesses are there. But because the government banned open religion for so long, groups are cautious.
I would suggest enjoying Cuba without the Kingdom Hall. If you visit during the Memorial, you are only required to attend if you you are "anointed" and need to eat the crackers and sip the wine, but isn't that something someone so spiritual knows how to do on their own?
.....or just go and hope to run into the JW's with their cart. I mean- preaching the word is so important. Of course you will find them doing that work. They will tell you where the Hall is.