Biden isn't going to win FL. The Cubans won't vote for a Democrat no matter if it's Biden or Sanders.
Per CNN '16 Exits in FL:
Trump won Cuban Hispanics 54-41 (6 % of the Electorate in 2016)
Clinton won Puerto Ricans & other Hispanics 71-26 (10 % of Electorate in 2016)
And also, while Sanders praised the Castro regime, we also have to understand that Biden was among an administration that was dealing with the Castro regime, removed sanctions on that regime with nothing in return, thus just giving them to earn more capitals to strengthen its power, to allow Russian operations in Lourdes and allow the Chinese to conduct listening operations with their listening station in Berupal.
And also Venezuelan Hispanics will also remember Trump's handling of the Venezuelan crisis last year, which will help him to win among them or simply improve his performance among this group.