Mercado 28! Ask your concierge about the markets in the area then take the local bus (an adventure on its own) and do some shopping. Don't forget to barter! Also, the best food is in the little hole-in-the-wall places, so ask about those too, or find them on your own. Google translator will give you some phrases- learn a few in Spanish if you are so inclined. Silver and turquoise can be purchased at a great discount down there...
¡Ten viaje bueno! Y no toma. (Have a good trip, and don't drink.)