I just returned from 2 perfect weeks of Language Study tourism in this lovely and unique Colonial city, located in Central Mexico. A mid-sized university town awash with history and arts, numerous plazas replete with outdoor cafes and restaurants, and narrow cobble-stoned pedestrian streets free from cars and lined with bright colored houses--a perfect walking city.
The same quality makes it the perfect environment to relax and live for a few (or many) weeks, while studying Spanish language at one of several Language Schools. I very strongly recommend the "Escuela Mexicana": besides the obvious strengths-- centrally located, very professional, great value for the price (cheaper than many of its competitors), and vibrant social and cultural trips--it's the teachers that are truly impressive! I have studied at language schools elsewhere in Central America, but never have I encountered such a collection of highly educated and diversely interesting teachers (with university degrees in literature, philosophy, and history). This is especially valuable to the intermediate and advanced language study, as it makes the conversation classes that much more interesting. With one-on-one or small group classes tailored to ALL levels, and an age range of students 7 to 70, it has something for all.
I stayed with a family, as a homestay, which is common and easy to arrange through any of the language schools. Excellent way to get a deeper sense of the culture and place -- but be forewarned, as the city is set in a steep bowl of a valley, many houses are quite a steep climb up narrow streets at 6000ft altitude, so if you are not in good shape make sure you stay somewhere central.