I don't budget for food really. I book where I want to eat, which is almost exclusively table service & it costs what it costs. Of course, if there is a discount available where I happen to want to eat, then I'm absolutely going to take advantage of it. Most days we'll eat 2 table service meals & get snacks if/when needed. Occasionally we'll have 3 full meals a day, but normally that ends up being too much food for us.
I did recently do some estimating for my upcoming December trip, for the sake of comparing the TIW discount to the new AP discounts. We're definitely better off just using the AP & not buying TIW this time. I think we'll end up right around $2000 after discounts, taxes & tips. That is for myself & my 12 year old son for 13 1/2 days. It's only for actual meals though & doesn't include snacks & treats. So, maybe it'll end up closer to $2500. That doesn't include our 2 dessert parties either as they're already paid for.
I also, pay for everything on vacation with my Disney Visa, so we'll get 2% back on all of that.