The Hierve El Agua [1] tourist
cabañas ecoturísticas have in the past provided the key for a restful one- or two-night stay. The several clean and well-maintained housekeeping bungalows, with shower-baths and hot water, rent for about $7 per person, or around $40 for up to six in a bungalow, with refrigerator, stove, and utensils.
For food, you can bring and cook your own in your bungalow or rely upon the strictly local-style beans, carne asada (roast meat), tacos, tamales, and tortillas offered by the parking-lot food stalls. In any case, fruit and vegetable lovers should bring their own from Oaxaca City [2]. Produce selection in local San Lorenzo village stores will most likely be minimal.
Links:
[1] http://www.moon.com/destinations/oaxaca/oaxaca-valley/east-textile-route/hierve-el-agua-springs
[2] http://www.moon.com/destinations/oaxaca/oaxaca-city