You mentioned Sanborn's and Mike Nelson...... when my husband I started driving down to San Miguel de Allende from Seattle in the mid-90's we used Sanborn's insurance for the Mexican part ( US car insurance would not cover driving into Mexico) and it always included the most comprehensive trip route I ever used. A book of every turn, every detour, every town that we would pass through on the way down from the Mexican border. So comprehensive that we found the navigator ( whichever one of us was in the passenger seat) never looked up or out as we were so busy reading the directions......I was the worst at it as I got car sick. In the few years we used Nelson's trip route book ( each book put together custom based on your trip) we only found one mistake..... he said turn right...but the signs had us turn left...........