I've got nothing on South Beach (oddly enough).
However, in Key West I recommend the following:
Louie's Backyard, this is one of Jimmy Buffet's actual hangouts and has amazing food and service.
Grand Vin, wine bar located on Duval street. You buy by the bottle and can sit on the open air porch. Very relaxing.
Hemmingway House and The Light House, both are very neat and a refresher from the touristy areas.
Southern Most Point, this goes without saying as no trip is complete without a picture in front of it.
Salsa Loco, on Duval Street it is very reasonably priced mexican food.
While the conch train will get you around and show you alot of the sights it is on the pricey hokey side.
No matter where you go in the Keys when you get to Marathon just hit the gas and don't stop until your on the next bridge.
However, in Key West I recommend the following:
Louie's Backyard, this is one of Jimmy Buffet's actual hangouts and has amazing food and service.
Grand Vin, wine bar located on Duval street. You buy by the bottle and can sit on the open air porch. Very relaxing.
Hemmingway House and The Light House, both are very neat and a refresher from the touristy areas.
Southern Most Point, this goes without saying as no trip is complete without a picture in front of it.
Salsa Loco, on Duval Street it is very reasonably priced mexican food.
While the conch train will get you around and show you alot of the sights it is on the pricey hokey side.
No matter where you go in the Keys when you get to Marathon just hit the gas and don't stop until your on the next bridge.

I mean Peapod check this site out 