Hiya
I would second the Mallory Square experience, the hour before sunset is fab. They have loads of street entertainers, and a great place to get a frozen cocktail. Also try Sloppy Joe's (Ernest Hemmingways old hangout) for a sloppy joe sandwich (mmmm) go and have your photo taken atthe southern most point of America, it is a photo worth taking,also there is a tribute to all the Cubans who have lost their lives trying to reach the USA. There is a Butterfly house, which is pretty, also you can go to Hemmingways house. to see the six toed cats. That is all at Key West To see all this you can buy an all day hop on hop off trolley bus ticket. At key largo there is the John Pennecamp National park which is a national park for the ocean protecting the coral reef, theyhave glass bottom boats, snorkling and scuba diving trips, there is also the theatre of the sea, which has dolphin shows etc. if you have seen the film, The African Queen, the barge is based at Key Largo Also as has already been mentioned the drive over to the Keys is fab. the seven mile bridge leave you gob smacked, also on your way down you can stop off at the Everglades and have ago on the airboats. As you can tell i loved the Keys it was most definatley worth the drive. Any other info needed just message me.
Hope this helps.
Ali
Ali