There are hot zones, yes. Border zones are less safe, Michoacan (minis the capital) are not a good place to visit either. Celaya as a city should be avoided, but the Rest of Mexico can be reasonably safe, especially the tourist areas.

Mind you, I've visited Celaya (and Michoacan) countless times and I've seen some shit, but I never really was worried for my safety. Stay in the main roads, tourist areas, you'll be fine.