Know that Avance will be selling its signature lamb burgers outside the restaurant at 1523 Walnut. And Oyster House will be selling lobster rolls on the 1500 block of Walnut - and Luke's Lobster will sell 'em on the 1600 block, as will Happy Rooster. Capital One will offer free cotton candy on the 1600 block. The Prime Rib will sell prime rib sandwiches on the 1700 block. Food trucks will park on the 19th Street side of the square.