The meat used for the barbacoa de Borrego is lamb, and it's lighter in color and slightly sweeter than the traditional beef used in most barbacoa found in the finest taco joints in Houston. It makes for a great taco, whatever the time of day. The lamb is slow-cooked in traditional Mexican spices until it falls apart. In a homemade corn tortilla smeared with refried beans and topped with nothing but chopped onions, cilantro and hot sauce, it is one of the best tacos you'll ever eat — and at $2, one of the cheapest, as well. Pity it's available only on weekends. Readers' Choice: Taco's a Go-Go