The Norm

All I can say, Guido, is that in the many years that my wife and I have been spending a month in Zihua we've never felt concerned enough about safety that we wouldn't bring our grandchildren down to visit.
I believe that, unless you're either involved in the drug trade -- or in trying to stop it -- the worst thing one might experience is seeing the occasional heavily-armed police and military patrolling the streets, or perhaps seeing the aftermath of a crime. (I noticed a bullet hole in a wall a few years back.)
If you exercise the same kind of caution you would in any sizeable U.S. city, you are very likely to feel nothing but safe in Zihua. You'll find the "vibe" a wonderful, I think unique, blend of old Mexican chill and charm with growing-city energy. And the people couldn't be nicer.
So...go for it!