Agua Blanca is a very calm village close to Puerto Lopez and part of the Parque Nacional Machilalla. It is a catholic community and they manage the little tourism they get communally. The main attraction is a pre-incan 70% sulphur bath and the archeological sites of the Mantena people.
The entrance fee is 5$ and includes a local guide who will show you around the village for about 3 hours.
You can get a direct motortaxi for $4 from Puerto Lopez or take a bus (0.25$), drop off at the entrance of Agua Blanca, and start walking. It's 5km, but the few cars on this road usually stop and take you if you put up your thumb.
All this is usually included in the little tour with your guide.
Longer treks into the mountains and rainforest are possible.
There is a little shop near the museum, where prices are not too inflated.
Food is a bit overpriced ($5 for a meal). First negotiate or bring your own if you can.
You can rent a cabaña for $10 a night or camp at the dedicated campground for $2 (no water at the campsite, but freshwater showers and toilets are available at the lagoon).
Same as get in. Pay too much for a mototaxi or start walking and hitch a ride.