Growing up in South Florida, we went to the keys a whole bunch when I was a kid. The keys I'm most familiar with are Key Largo and Key West. We actually went to Key West 2 years ago as a destination on a cruise. It's very walkable and dog friendly, lots of restaurants with outside seating on Duval Street. Went to one bar right off Duval that let dogs inside, think it was called the Porch. If you make it all the way down to Key West, there are tons of chickens roaming the streets and Polydactyl cats. Definitely a fun place but be prepared for the heat, even later in the year it gets quite hot.