Ok I have the location. It is just a few hundred feet south of the San Miguel toll booth. There is pemex 9917 (if its still a pemex, opposite the turn, there is also a federal police station there.
Coordinates are N 25.973491 W 109.035518
The property is less than 1/4 km down the side road. Accessible from both sides of highway
N 25.968461 W 109.034240
I will find out if its usable with dry camping this season and post here. I have giving orlando the address of this forum, maybe he will register and answer questions