Ermagersh, YES!
Marker 88 has ambience as well as great food and drinks! It's a must-visit (thanks Gregory, for the suggestion!)
The Twisted Shrimp is another good one. The feel is so "Keys", the food is bomb.com.
Lorelei has a gorgeous atmosphere, lots of space, a delicious menu, and a giant mermaid. Win!
If you have extra time, check out Bahia Honda and/or Key West.