As noobs to Mexico, we took the leap and are quite happy. Left Nogales on the 12th of December, and saw NO Rvs on the road to Mazatlan. You definitely are on your own. Mex 15D is under construction everywhere. You can drive 50 miles on US style interstate, then the next 50 miles suitable for a donkey. We are now at Lake Chapala, and it's barely dented with weekly or monthly Rvers. Mostly Canadian and American permanent residences. We had planned on staying a month, but after visits to the small towns in a week's time, maybe are thinking of back-tracking to the Lo de Marcos area on the coast.
To sum up our experience thus far, we under-estimated everything. Had to buy a 30amp regulator from the local electrician, 195 bucks. Should have bought it in the US before we left, and a surge protector. That's still on the list to get. As one that is used to traveling 500-700 miles a day in the US, down here, 250 miles before dark is a good goal.
Otherwise, the people are great, the food is really cheap, the weather here is wonderful. Will we do it again? Probably, but we get antsy and staying in one place is difficult. But, traveling around a lot is difficult too with the roads and those **** Topes~!