If you happen to be in Guanajuato during the weekend - try joining a "callejonada". It starts on Friday, Saturday and Sunday around 8:00-9:00 P.M in front of the San Diego Church on the Jardin de La Union. 

A group of singers and musicians, dressed in traditional customs, begin singing and playing. The people around join them and after a while the singers and musicians, leading the crowed, start walking through Guanajuato's narrow streets, playing and singing, stopping from time to time  to allow the people to have some wine, while they keep singing and telling stories. This events are free  - you are not required to pay for participating in the walking and singing but only for the wine you drink, if you wish to drink. It is a very pleasant way to spend the night. Yes, it is a little bit touristy (though more domestic tourists then foreigners!). You do not need tickets for the Callejonadas so avoid individuals offering to sell you one or demanding payment for a "Callejonada"!!