Looking at the maps, in going from Durango to Peidras Negras it is about 33 miles less taking Mex 30 instead of Mex 40 and connecting to Mex 57. Anyone have any insight into whether the mostly 4 lanes of Mex 40 are worth the 33 extra miles that Google is suggesting? I am not one to even get to the speed limit in many situations.
Also, I don't see much about where folks stay the last night before crossing back to the US via Piedras Negras. Thoughts and Experiences?
I can't provide much help other than to say a lot of people used to avoid the Piedras Negras route to avoid going through Monclova as they say the cops there are among the worst you might encounter in Mexico. I don't know if that is still true. If you go to Columbia there are RV stops around Saltillo in the Church book and Paul & Helen said they stayed in a truck stop Pemex near there which I think might be at 25.59427 -100.87925 -see on Google Earth - but not sure as we did not stay there. There are other Pemex stations but I don't recall any that were big enough for us - though they might be big enough for you - don't know about 24 hour security. Others will probably know.
After we crossed at Columbia we spent the night at the Texas Welcome Center on I35 - they tell us the toll route 255 will take a picture of your plate and send you a bill as there is no toll booth.