kroozer 

I have lived in Mexico for most of last 20 years, in Nayarit, to the west of San Miguel. I don't know that area very well, but the weather in the highlands is great all year-round. No reason at all not to bike, in fact it's a great way to get to know the area. I would make pretty much the same recomendations as in the US. Stay off the main 2-lane highways, they are narrow, heavily-travelled, and extremely dangerous. Secondary paved highways are usually fine, the problem can be finding enough of them. Lots of great gravel roads if you're into that. Urban commuting is fine, too, although the streets are generally pretty rough (I use an mtb). If you can, take a road bike and an mtb. You can probably borrow or rent an mtb locally. There is probably a local group of recreational riders that you could hook up with.

The drug violence is getting to a ridiculous point, and I don't recommend Mexico to anyone for a vacation. On the other hand many areas are peaceful, and I haven't heard of any problems in Guanajuato state. However, if you're driving down, the northeastern border areas are a war zone.

I live in a small city (pop. 400,000) which is also the state capital. Like all the Pacific coast states Nayarit is a traditional drug-producing area, but violence was always minimal and was limited to people involved in the drug trade. Last year we had over 400 drug-related murders, many of them innocent people, and about 150 so far this year. There was a big shoot-out yesterday on a main boulevard with automatic weapons and grenades in which six narcos were killed and a couple innocent bystanders wounded. The government is worse than useless, the cops and politicians work for the narcos too. Kidnapping is an industry, extorsion and robbery are becoming common, and everyone is afraid. This is a beautiful place and life here has been great up till now, but we're seriously considering leaving.