I just read in today's Correo (one of Guanajuato's newspapers) that this year's International Cervantes Festival (number 38) will last an extra week, so we'll celebrate for 26 days.
The mayor said the starting date for the festival will be announced in the next week or two. I'll keep my eye on the news and will post the dates as soon as they are announced.
Here is the link to the article (in Spanish):
I hope lots of you can come and take part in the festivities!