Our first trip happened in 2003. No GPS. No Church and Church. Triple A maps for there were not so good. We bought Mexican maps as soon as we could find them, the Guia Roji maps. We relied on our Sister in Law's pocketmail emails to get through cities such as Puerto Vallarta and Hermisillo (where's that? okay, only a city of three quarters of a million people then) but got lucky as we tagged along behind a convoy of about 25 RV rigs. Think you're going to pass them all? we never even tried. Pocketmail? for us we used public phones for it, with the 1970's technology that at the time was popular with sailboaters with sat. phones. Two or three times we neded to back our motor home up at intersections, the only way to get turned around. We drove through the cobble stoned street near the Malecon in P.V. that first time, after missing the all- important but obscured sign, and ended up going backwards through one tunnel, going north instead of south. Had to ask directions from locals certainly more than once. Our best couple of days that trip were when we were with friends we had made, an American couple we had met in Los Mochis. But they stayed at the campsite south of San Blas and we were on our own again. But loving it!
Hope you make it into Mexico, you should go, and will enjoy looking back on your experiences as we do, from time to time.