Are they driving? How can you move that many people, that fast, all the way across Mexico. That is a logistics nightmare, especially considering the quality of the transportation resources down there.
Yes, they are being transported, there are pictures on other threads of it. Although I lack the evidence to state it as fact, I believe this is all organized to influence the elections.
When the cameras are on, they walk. Otherwise, it's motorized transportation, all the way!