There are several thermal springs due to the volcanic belt in the area of GTO, SM and DH. The two that I am familiar with are: Balneario Escondido Place and La Gruta. These are not spas as we know day spas in the US. These are true mineral waters heated by the earth, they are wonderful and unique. If you google the names several people have posted on the internet about them. Escondido is three pools all connected by way of stairways. The first pool is warm, the next warmer and the third pool is quite hot and has a dome ceiling built over it. La Gruta has more services such as a restaurant, lockers, showers and you can schedule a massage or a facial. They also have two pools that are not heated for lap swimming or cooling off. There is one pool that is warm and at it's far corner there is a tunnel to navigate thru. It takes you to a large round pool with a domed ceiling, a few times per hour a waterfall comes from the ceiling. Everyone lines up to let it splash down on their neck or back. I have taken my mother and sister and they had a wonderful time. My husband and I took our young adult children and their friends a few years ago at spring break, they all had a great time and were not ready to leave at the end of the day.
Spanish Language schools:
There are several in GTO as well as in SMA. The only one I have experience with is Escuela Mexican. We studied there for several weeks in 2007. My husband and I had little knowledge of the language and found taking too many classes was overwhelming and exhausting. We would take 4 classes a day and then need to do homework and practice in the evenings. This did not give much time to enjoy the city. Our daughters had some Spanish in school prior to coming so they had an understanding of verb conjugation and past, present and future tenses. This helped them become fluent in speaking and writing. I would highly recommend them, just don't take too many classes and restudy basic English grammar prior to starting classes. They refer to the English grammar terms and if you don't remember them it just makes it more difficult. http://www.escuelamexicana.com/
Hope you enjoy your stay at Casa Chan and in the beautiful city of Guanajuato.