Things to do in San Miguel

There is a tourist office on the main square, but you will want to research before going - I don't have any "must sees" other than the area around the main square, but you can easily find lots of recommendations on the web. Did not have time for any side trips, but be aware that this is rather a remote location that offers a slow pace with old and new mixed. One thing I would have wanted to know before going: I was there in January 2009, and was unprepared for how cool the weather gets at night - down into the 30's. Daytime temps reached high 70's/low 80's. One of the down sides is that very few hotels or facilities offer heat, so ended up in bed under the covers at 7 pm -- too cold to do otherwise, even with two space heaters provided by my $350/night hotel. The downtown area is fun to wander through, several cathedrals, lots of shops and restaurants, and the main plaza is lovely. Locals advised that Guanajuato's historic downtown area is just as nice.

San Miguel is wonderful, but you won't be escaping the cold as it is high in the mountains in what used to be the silver mining area. (read "Rain of Gold" about a family from there who immigrated to the US). What to do: eat and shop, even if you don't like shopping, and be sure to include the central market (downhill in the more authentic part of town). As you look at the wonderful church in San Miguel, you might want to know that the untrained architect saw some pictures of Gaudi's Sagrada Familia in Barcelona and copied the mood.
Six weeks is a long time; maybe you'll want to take a few Spanish classes or cooking classes, in English; San Miguel has a lot of ex-patriots.
I'd also take a few days to travel for an hour over the mountain to Guanajuato with its Eiffel designed indoor market, its Cervantes museum, and its Diego Rivera house and museum. If you have a car, going or coming from San Miguel, you might want to stop in Quertero and walk its central historical area.