Surprisely, there's far more good safe places than what you stated. The border cities tend to be cartel controlled and obviously there are cartel controlled areas within Mexico. Mexico city is the hub of government power and the highland areas around are very safe. When traveling you need to know the area, its crime rate, and as much of its culture as possible. We use to travel down to Baja all the time. Only once did we have an 'incident', where we were pulled over by 'federalis' and extorted of money. I was prescient enough to invite my Mexican friend along and he negotiated us on our way. We gave some money. Extorting poor college kids isn't a big prize. We never drove good vehicles to Baja. It was always junkers. We dressed somewhat like the Mexs did too. Not like a big city gringo, but Tex-Mex.