This caravan is NOT preparing to cross the border (into USA) on Christmas Day. They are just inside southern mexico after crossing from Guatemala, and are weeks or months away from the U.S. border (unless they get bus transport). The audio on the video provided is a bit unclear but I believe the next stop planned is Oaxaca or some place east of the capital.
This is of course blatantly illegal activity even under laws of mexico, let alone laws of U.S.A., but nobody seems prepared to enforce these laws.
Further to the above, this caravan is just 10 miles inside mexico, west of border crossing (w Guatemala) of Tapachula (mentioned in video at link) ... there is a small town of Alvaro Obregon, and I believe this is the location of caravan, not another Alvaro Obregon which is a suburb of mexico city.
They are not even 1% of the way to the U.S. border, and about 3% of the distance to mexico city (which is roughly one third of the total distance to U.S. border). Unless they get bus transportation, they are going to be walking for at least eight weeks and perhaps closer to twelve. There is a strong communist vibe to the commentary on the video.