My stay in Oaxaca is almost over. At the border, when I nodded after the agent said something about "mountains/Montaign" I was able to get the two vehicles in on one sticker on the Van windshield.
No questions or problems after clearing the border.
Virtually none of the bike I have seen here (100's even 1000's) have tags at all. No one has asked about insurance.
Of course, I've been in school and used it very little. Had I known, I wouldn't have bothered to bring it.
The rear rack and topes do not get along. I'm going to store it inside the van for the return trip.