My wife and I have traveled extensively by road through Mexico over the last 3 years and there are some basic rules you want to follow while driving in Mexico.
1. Never take you eyes off the road. The roads are narrow and just beyond the edge of the pavement may be 3' deep concrete drainage ditch, cliff or other equally undesirable obstacle. There can be livestock or a broken down vehicles around any corner at any time and there is very little margin for error.
2. NEVER DRIVE AT NIGHT! I will say it again. NEVER DRIVE AT NIGHT. There are lots of black cows that wander the roads at night. I know this because we have passed many dead ones, some accompanied by wrecked vehicles. Also at night you are more likely to encounter truckers traveling at breakneck speeds, smugglers or other undesirables.
Never stop for any locals on the road that are attempting to flag you down. Flash your lights and keep on going. If they are gringo's use your best judgment.
It is generally not advisable to camp on remote beaches alone. This is especially true if you are near the US border. You will be much safer if you have two or three rigs.
My last rule is to start looking for a gas (Pemex) station when you reach 1/2 tank. There are occasions where the gas station will have a sign that says they are out of gas but there will be a very friendly guy selling gas from the back of his pickup truck at premium price.
If you follow these rules and always be aware of your surroundings you should be fairly safe. If you are ever somewhere and things start to feel weird the best course of action is just to move on.
You will also want to get Mexican insurance. If you get in an accident in Mexico without it you will get to wait in jail until the police determine who was at fault. If you are found to be at fault you will stay in jail until the damages are paid.
Keep in mind that if our news published every drug related shooting that happened in the USA, Mexico would seem safe by comparison.