Here's an interesting stat I saw for referance. There are 9 million passenger trips per year on American airlines. Oh, I know, get a horse. LOL
Here's an interesting fact I saw for reference. We are talking about criminals, not tourists.
For all I care, "Sheriff Joe" can put 'em all in one big chain-gang and march 'em across the border.
If that's too much for your tender sensibilities, then stick 'em on a bus. Plenty of Americans travel by bus every year. If it's good enough for us, it's good enough for them.
For that matter, I imagine a railroad would carry a lot more than a bunch of busses. Let 'em build the tracks, then let 'em ride the trains back to Mexico.
Last Stop, May-hee-ko City, ALL OFF!