C.D.
I second the recommendation for St. Augustine. My husband took me there for our anniversary a couple years ago and we had a great time. It was great because almost everything is within walking distance, which makes it that much more romantic at night. Some nice sightseeing, romantic horse and buggy rides at night as well as some nightlife and fantastic dining. We stayed at The Augustin Inn. It was wonderful. The breakfast was great and they had a beautiful farmers porch that you could sit on and eat in the morning. The rooms were nice, we had a nice corner jacuzzi in ours. I think it was the Imperial Room. Their rates are very reasonable as well. Here is their website:
Enjoy!