My favorite cheap eat in the Orlando area is a hole-in-the-wall dim-sum place called Ming's Bistro in downtown Orlando. The food is tasty and filling, and it's easy to get a meal for three for under $20. The appearance/service of the place isn't memorable, but the food is worth the trip. I've taken many visitors there and they have enjoyed it.
More info:
Ming's Bistro
1212 Woodward St # 6, Orlando, FL 32803-4173
Open Daily 10:30am-9:30pm
(407) 898-9672