If you start in Calexico with Google Maps, the street you will be on is Imperial Ave. as you cross the border the road you want to be on is Adolfo Lopez Mateos, that turns in to Highway 5, which is the highway to San Felipe on the map follow Highway 5 to Mexican Federal Highway 2D dont take highway 2 in town it will take you forever 2D is what you want to San Luis. Pay the toll, get on the highway it will turn into highway 2 and take you to San Luis, pay the next toll and stay on that highwat thru town, its called avenida Obregon in town. Just stay on it, it untill you come to the exit to El Golfo, turn south and you will be on Highway 3 to El Golfo. The map outside of San Luis looks screwy and for that matter so does the map south of Mexicali. Just get on Google maps and follow 5 to 2D then to highway 2 and dont pay attention to the other roads.