I agree with lynninpa, almost all TS in the park are informal. Even Hollywood Brown Derby is informal. Even though the room is elegant, with white linen tableclothes, etc., most ( if not all) of the diners are in park attire. (tank tops, flip flops, shorts, etc.) This is entirely okay. The more formal (dress code) TS are located outside of the park, with the exception of V&A.
I agree with this statement!! I believe that every restaurant in the park with a few exceptions are informal. The staff knows you are coming in from a long day at the park.