originally from north of where we live and I have lived in the us as well as here. We live in mexico state, one of the many pueblos in the toluca area, I don't recommend it in this area as it's pretty rough. No narcos though.:) We are thinking of moving to san cristobal de las casas, chiapas as we would go further south. Pretty much all of my inlaws live here though so that's why we have stayed this long, plus we have a house.
San Miguel de allende is beautiful but expensive, which is not a worry if you can afford it. It has been mentioned the foreigners there don't mix much in the local language, etc. and is true. The chapala area also has many like that. Where we live there is no english, I like that but again it's not a safer area. For the most part high foreigner areas are the safest, the police "take care" of those areas more than those of poor locals.
Guadalajara extortion and that type of stuff is on the rise. It's still not where more northern cities are, but is picking up and there were recently a couple of narco shoot outs in chapala.
I'm not trying to scare you to death, just make you aware that things are not like they once were. Just be prepared to hear of such stuff.
You might research into san cristobal de las casas, chiapas or merida, yucatan. Both places are south, beautiful and safe. I have had several people from guad tell me they are looking at san cristobal, merida is very hot.
Good luck, I know you will enjoy it.
Also, this forum has people from the guagalajara area. Mostly chapala and there are some from sam miguel. You could probably read some there and/or ask some questions:
http://www.chapala.com/wwwboard/webboard.html