Depends on when and where you want to eat.
If you want a character meal you can probably forget it.
If you want to eat in a park, you may not be accommodated in peak mealtimes. Your best bets at Epcot would be Marrakesh or Nine Dragons. If you're not OK with those, you'll probably need a reservation or be prepared to wait. MK has only six table service restaurants at dinner (unless the overflow at Diamond Horseshoe is open). Your odds of getting in a restaurant there without a reservation are not good.
If you're good with leaving the park and going someplace like Downtown Disney, it might be easier.