About half a kilometer south of town is 
Las Cumbres (tel. 5399-0029, 7 a.m.–7 p.m. daily), a superb establishment harboring steam baths, beautiful accommodations housed in quaint red-tiled-roof cottages with mountain views, and a restaurant (all meals daily) serving mostly Guatemalan dishes but also sandwiches and wine.
Thermal pools were in the planning stages and may be up and running by the time you read this.
Its 11 rooms range $33–47 d and have nice wooden furnishings with warm wool blankets, private bathrooms, cable TV, CD player, and plenty of rustic charm. Some have their own in-room hot tubs.
If you don’t want to stay but just want a steam bath, you can have a private sauna for $3.50. Room rates include sauna access. There are also a squash court, pool table, and a small gym.