For budget restaurant eating, you've got some good choices. Just remember to order small and share at first. If you want to get more food after you see the portion sizes, order more.
Most of the condiment bars at counter service restaurants only offer packets or dispensers of ketchup, mustard, mayo relish, etc. But some (like Cosmic Ray's) have more, like fresh lettuce & tomatoes, onions, pickles, peppers & hot cheesy sauce (for cheesy fries). At one of those restaurants, you will get more food for your money if you like your sandwich piled high. Our kids eat that stuff like side dishes!
At some of these restaurants mentioned, like Rainforest and Sci-Fi, most appetizers are huge. We sometimes order one appetizer, one salad, one entree and one dessert and leave a place like that with two of us (good eaters!) absolutely stuffed!
And this let's you sample a lot without breaking the bank. Skip the expensive beverages and drink lemon water, if that's not too much of a hardship - it saves our family about $10 per meal. Now that our kids are getting bigger and have more adventurous, adult appetites, it's getting even easier to share around the table in restaurants.
Also, the buffets are wonderful but they do add up. If you arrive around 3:30, you will pay lunch rates and get to have seconds at the dinner buffet, with more variety. If you go to a breakfast buffet, go at 10:30 and make it a big brunch.
Have fun with the restaurants, too. Don't hesitate to stop into one during the quieter times between meal hours and see if you can be seated for dessert only, without a p.s. Then you get to try the place without dropping a bundle. For our family, it's $10 just for Mickey bars! So $20 for a couple shared desserts + tip is worth it for the ambiance. It also doesn't take nearly as long to be served as cooked-to-order food.