You said you were traveling in both NM and AZ. The info briansue gave you about Palomas, across the border from Columbus NM is the best. We have crossed there several times and the building with all the official offices backs up to the border fence, just inside the gate on the west side. I would do just as he said, park in the lot on the American side, directly behind the Mexican office and walk over to ask how they want to do it. They will look at the size of your RV and then tell you what they want you to do.
