Lots of photos at the linked article. Those numbers are expected to double next year. How
they get north thru Mexico isn’t supplied but they don’t just walk those hundreds of miles.
They ride on top of trains...do a search, many pictures will come up...I have seen recent pictures of the tops of train cars literally covered with people. The Mexican officials don’t care if they stay on the train and come to the U.S.
I tried to post a picture, failed...anyway the trains are known as “beast” train.