Mike.......
After dealing with Mexican customs at the border, where you will most likely get a green light, the only required stop will be the agricultural checkpoint at El Doctor, about midpoint between the border and the El Golfo turnoff. They WILL look in your coolers and ask what you have. We usually have some traveling snack fruit like grapes, cherries, green apples, etc. I just tell em what we have and they might look but usually happily wave us through.
Be careful with the town of El Golfo. The turnoff to the Coastal Highway is well marked and about a half mile before entering the town proper. The cops there are well known bandits and they will stop you for no reason at all. They will check you out, ask a few questions the determine if you are weak enough to fall for their lying shit, usually speeding or running stop signs that never existed. They will demand the now usual hundred bucks USA. You might get em off your back if you demand to go to the Police Station which is right there on the north edge of town.
My policy is to AVOID El Golfo entirely. They have nothing you need that you can't get in Penasco. Be sure that you fuel up before leaving the border. There is a Pemex station in El Golfo.
As you get close to Penasco you may be stopped by a road block by the Federal Police. They might ask a few questions then wave you on. They are looking for the hardcore criminals not you.
Have fun!
JJ