Key West Valentines
Haven't tried it yet personally, but from the rave reviews on this board (and some others) I would suggest maybe Better than Sex for dessert. We've walked by it a few times during the day, but we have yet to make it back there in the evening for dessert. It's definitely on list of things to do the next time I'm down there.
If you want to go out to dinner, start calling places! I made a reservation 2 weeks ago, and already couldn't get my preferred time some places. Not sure if it's booked yet, but I've heard Latitudes on Sunset Key (ferry ride from Key West) is really romantic. I decided to skip it since it's all about outdoor dining and I wasn't sure what the weather would be...