Violent crime in Mexico is less of a problem than in the United States or Canada. Guns are not allowed. Mexican law is hard on violent criminals. You can feel much safer walking the streets in Mexico than in most other cities in North America. The larger cities such as Mexico City have a crime problem like any large city.
Mexican people are generally friendly and helpful.
They almost always return a greeting, and usually with a smile. Speak a little Spanish, and they will go out of their way to be helpful. The border areas do have problems, but some of the horror stories you may have heard are greatly exaggerated. Imagine the crime stories that could be told about one evening in Los Angeles. Corruption exists, but it is not as bad as you might think.