Hierve el Agua, Oaxaca
Probably the easiest way to see Hierve el Agua is to do so by tour vans running out of the city of Oaxaca. Invariably, they'll be all day long affairs with side trips to a Mezcal distillery, Mitla, Teotitlán, or some other tourist hotspot. If you just want to see the springs, you can rent a car or hire a taxi for the day. It takes about an hour and a half to drive both ways. If you are planning on driving yourself the route is well marked. First, head east out of the city on Highway 190. Once you get close to Mitla just follow the signs to Hierve el Agua. The pueblo of San Lorenzo Albarradas has put up a toll gate on the road to Hiever el Agua. The toll is MX$10 a person. By all accounts, this is an illegal obstruction of a state road on the part of pueblo, but given that it's such a small fee, it's best to just pay it and be on your way. Besides, illegal or not, you're not getting past the toll gate without paying. In addition to the illegal toll, entrance to the park, which is run by the San Isidro Roaguia pueblo, is another MX$20 per person.
The cheapest and most adventurous way, however, to get to the springs is to take a camioneta (MX$30) from Mitla, the closest large pueblo to the springs. Figure on the trip from Mitla to take about forty-five minutes to an hour. But first you have to get to Mitla. Mitla bound colectivos (MX$20) depart from the sitio southeast of the Abastos market and second-class buses(MX$14) from the Central north of the Abastos market. These same colectivos and buses can be flagged down at the northeast corner of the baseball stadium (De Los Derechos Humanos and Eduardo Vasconcelos).
If you want to stay overnight at the park, modest but clean cabanas can be rented for MX$100 per person for the night. As for food, there's a dozen or so food stalls lining the park, or you can hike the short distance back to the pueblo and buy food from one of the abarrotes.
Also, if you've been hankering for some home distilled mezcal and you're driving a rental or being driven by a taxi, stop by Señor Martinez's place on the side of the main road, about twenty minutes outside of Mitla. Most likely, you'll see a small plume of smoke, the cores of Agave plants cooking, before you come upon his humble distillery. Other than his roadside distillery there's nothing around for miles. He will be happy to show you his cooking pit, stone wheel for crushing the cooked Agave, fermentation vats, and finally the distiller. One liter bottles of the primo stuff, two year old tobala, wild agave, cost MX$140.