Here are my St. Augustine restaurant recommendations, based solely on my personal preferences... and 20 years of enjoying their cuisine:
For Lunch
Café Alcazar (25 Granada St, Saint Augustine, FL 32084-4387) is a true hidden gem…and is definitely off the main tourist path. It is a small restaurant located in what was once the deep end of the world's largest indoor swimming pool, now the Lightener Museum building. The food is quite good (I love their curried chicken salad.) and the atmosphere is absolutely unique and very conducive to conversation. They don't take reservations and only serve lunch. If you have trouble finding them, you can phone them at 904-825-9948.
http://www.thecafealcazar.com
For Dinner
Old City House
http://www.oldcityhouse.com/
Outstanding breakfasts and dinners. Located just steps away from the Casa Monica.
The Raintree
http://www.raintreerestaurant.com/
Purple Olive
http://www.purple-olive.com
The Reef
http://www.thereefstaugustine.com/index.html?
The food is very good, and the ocean views are even better. Be sure to arrive before sunset (or for Sunday brunch) for best views. Their Sunday brunch is the best in town, IMO. Request a window table when making your reservation.
Saltwater Cowboys
(My personal favorite for ambiance and value combined)
http://www.saltwatercowboys.com/
Gypsy Cab Co.
http://www.gypsycab.com/
Creekside Dinery
http://www.creeksidedinery.com/rest.html
Le Pavillion
http://www.lepav.com/
And, for a special treat...you should try Collage
http://www.collagestaug.com/ It is strictly a special occasion restaurant, but if you like good service, warm & relaxing ambiance and a creative, eclectic menu, this restaurant is a wonderful experience. They do everything right!
Honorable Mention
O'Steens
(Perhaps the best shrimp in town. ZERO ambiance, no reservations, reasonable prices)
http://tinyurl.com/2qtxgd
Barnacle Bill's
(Very good shrimp, reasonable prices, family atmosphere)
http://www.barnaclebillsonline.com/
You'll notice that I did not mention the Columbia restaurant. IMO, their food is good, but not as good as any of the other restaurants I have mentioned.
Also, it is somewhat of a tourist trap and one of about 6-8 other Columbia's around the state. This may qualify them as a chain restaurant. I know a lot of people eat there, but the other restaurants I have given you are all better.