There are several of these restaurants around the city . . . this one was in the Puerto Madero neighborhood.
It cost 21 pesos (US$7) per person for all-you-can-eat grilled meat (chicken, sausages, pork chops, etc.), all-you-can-eat salad bar, a soft drink, and dessert -- a great place for hungry eaters. You walk right up to the grill, point to the type of meat you want and the cook puts it on your plate. The price drops to only 15 pesos during the week (I was there on a holiday weekend).
The quality was good, but all-you-can-eat doesn't appeal to me that much for some reason -- it can be kind of a zoo, with people walking all over the place (to and from the salad bar and the grill).