Sadly, Big Thunder Ranch BBQ is closed for good due to construction of Star Wars Land in that area. It was a favorite of so many people and such a quiet area with great food and ambiance and I know lots of us miss it. The 'trail' it was on is shut off on either side, also, blocking that nice little shortcut.
If you are just now 60 days out, it is most likely that the reservations are just not loaded into the system yet, a super common thing at DLR. The only things that book up immediately seem to be Christmas or Thanksgiving buffets at the DLH and special event parties like last year's Halloween dinner in Blue Bayou. But otherwise you can practically get reservations next day, especially for smaller parties at lunch. Though maybe not the week after Christmas... I thought that was historically the most crowded time of the year.
And there are SO MANY great counter service places in DLR that you shouldn't forget about, Rancho del Zocalo is so pretty at night, great simple menu and practically perfect people watching at Jolly Holiday, the neon lighting and dinner at Flo's in DCA, soup in bread bowls at 3 places in the parks, the unique and refreshing menu at Paradise Garden Grill in DCA, and lots more!
I love the app because you can not only make reservations right there, but the menu is listed and you can use the map to locate the most appealing choices nearby.
Where are you planning on?
