Absolutely loved this trip. The drive down the keys is interesting, the driver gives plenty of information and insight with a quick stop at McDonalds to grab breakfast on the way. I did not pay for the Conch train, instead getting the free Duval loop which pretty much follows the same route without the commentary.
Hemingways house is fascinating, especially the cats who own the house along with the archictecture, sun and hot tropical rain - never lasts long. Completely different feel to Florida and Miami, may be a long day but worth the effort, if only for Kermit's Key Lime Pie.