Mama Stellas, bland pizza and pasta. Can't recommend.
Seaport Market, in hospitality building. Very good sandwhiches and breakfasts.
Calypso Smokehouse, good bbq.
Shipwreck Cafe, good burgers and bbq.
Just outside the gates is a hotdog stand. They have far better hotdogs at better prices than found inside the gates. Late in the afternoon, early evening this stand often has everything 2 for 1 including bottled drinks.
If you plan on being there an entire day from morning to night check and see if they are selling the all you can eat wristbands. If eating 3 meals there it will easily pay for itself and allow you to eat whatever you want along with free drinks all day.