On Sundays, when everyone is off work, this grocery store looks like the site of a fiesta. In aisles festooned with all-occasion pi?atas, shoppers -- many with kids in tow -- load carts with provisions for the week ahead. A lot of socializing takes place here. And eating, too. There is a nacho kiosk by the front door, and back in the corner an in-house tortillería. Few can resist slipping a still-warm tortilla from the bag, adding a dollop of salsa, and savoring a taste of home right there by the economy-size bags of rice and beans. On the shelves: chilies, various types of mole, cases of Tamarindo soda, and an esoteric selection of herbs, including cola caballo (literally "horse's tail," or shave grass), used to make a tea said to cure kidney problems.