As someone who was hijacked and kidnapped in 2004 and who has twice in the past year nearly been ambushed [each occasion when I had a vehicle], I would say never travel outside the town areas unless you know the area and where you are going. Travel with a local if you are going any distance. Never stop for anyone who tries to flag you down; go round any obstruction as fast as you can; if you break down or have a flat tyre, somehow get yourself to an inhabited area; if someone bumps into you, keep going; only carry copies of your official documents and nothing of value; keep vehicle doors locked; if there is an apparent police blockade, insist on seeing proof of ID before opening doors; don't travel after dark other than in well-populated areas; tell someone where you are going each day so that if you don't return the alarm will be raised; be careful when you stop for a break and check your tyres before you set out again, making sure you aren't followed when you leave; keep out of the barrios; don't stop in unpopulated areas; don't pick up strangers; make sure you have enough fuel to get you to your destination; learn the language and read body language carefully. Mostly, the people here are fantastic, but it only takes one to make your trip traumatic. Have a great time!