Like I said in the Xela's tip, these are awesome hot springs! The views from up there are breath-taking, and the hike down the mountains is incredible!! Almost 10 KM through vegetable-growing fields, with plenty of locals along the road ... nice!
If you decide to walk back to Zunil, just be careful when you are getting closer to town. You'll see houses ain't pretty, it looks like going through some sort of slum. Nothing happened to me, but you better watch out.
There's a Q$ 20 entrance fee, totally worth it!
Zunil is located in the Guatemalan western higlands, with great views of the volcanoes, and with some interesting indian villages nearby.