other than calling to check, since I know you're going to be at Fiesta Texas soon. . the Dining Plan center is just past the main entrance way on the right (before you get to the split off into the main park, but after you pass the "main street" area. It's basically the last building on the right, before you get to the main central plaza.
you won't be able to miss is. . but if you can't resolve before your visit, I'm sure they can help you out there