You don't have to get the fixed price menu. You can get any entree and dessert. The fixed price menu gives you an appetizer but your entree choices are limited.
Coral Reef had a fixed price menu when I was there last September, i got a heirloom tomato mozzarella cheese with balsamic, mahi mahi over rice with a dessert. You can find the menus for the various restaurants on Disney's website