I don’t believe that since the Mob has been in Mexico City for about a week. Trucks with people hanging all over them have been forbidden by the Mexican government.
Every picture I have seen where trucks are involved shows them moving at a snail’s pace. Even with people on them it does not change much. My guess is they are used more for a resting place than for rapid transportation.
Assuming what you say is true, it means that these trucks cannot go full speed and I doubt if they can even make 40 mph. This would mean that it will take 10+ days to get to Tijuana. And it has already split up, before the going got really tough.
Another thing to consider is that if they were really on trucks we would be hearing about deaths from falling off. Have you heard of any?
.
Ever been to Mexico?
Few vehicles can do better than 40 on most of their roads.
Only a fool would take their own car to Mexico.