General rule of thumb: if the locals drink the water, it is probably safe. If they don't, dont even think about it, unless you want to spend your whole vacation in the bathroom. In Taganaga, portable water is found in clear plastic bags, a lot like the cafeteria milk when I was in elementry school, only no straws included. A bag the size of the one I am drinking in this photo is 100 pesos. That is about 5 US cents.