Boathouse does have a grouper dish: Gulf of Mexico Red Grouper - Roasted Sweet Potatoes, Onions, and Arugula, Charred Leek Butter. California Grill has grouper in their cioppino dish but unfortunately it's a prix fixe menu there unless you're sitting at the bar. They also used to have a grouper entree but looks like it's off the menu for now.
When are you visiting? Florida red grouper season (gulf waters) runs January through July so you're probably more likely to find it on menus then.