I went to Miami (about 30 years ago) and while walking in the street on Shabbos met someone from my shul and his wife. since we were both “out of towners” we struck up a conversation. When I got back to new York they called me with a shidduch. Of course the story had a happy ending and I still thank them after each grandchild. So yes Miami is a great place to go.
Nowadays, the best bet for bochirim is North Miami beach. You can rent a private(kosher) house and pool there, which will accommodate 6-8 boys for about $450 a night. There are 5 shuls and a kollel in the neighborhood.