My wife and I were there last year.....unless you plan to fish or snorkel or dive, be prepared to do lots of walking....
Several famous bars are there, several local museums highlighting local history....people like Hemingway ...
If you are driving.... The trip down is pretty interesting....
You can see the railroad Flagler build about 100 years ago still standing almost all the down the highway....
We drove from Tampa to there....
The old US 1 paralleled the tracks for quite a ways. Was stationed down there in the early '50s and made he weekend run to Miami on a three-day liberty. Lotsa fun dodging the fishing sinkers coming through the windshield from the guys fishing off the bridge. They'd swing the rod back to cast and often wouldn't look to see if a car was coming.