I haven't clicked on your link yet but off the top of my head I'd say walking the length of Mexico would be no more dangerous than walking across most anywhere in the U.S.

My daughter and her boyfriend rode his adventure bike from LA to somewhere around the middle of Baja last summer and wonderful time.

I've been to Mexico several times and never felt I was in a dangerous situation. Of course, I grew up in some pretty tough neighborhoods, including San Fernando and Pacoima in CA and what's now call the 14th most dangerous in the entire U.S in Rockford Ill, so I know a bit about how to avoid bumbling into a stupid situation.

Street smarts is a good thing to have, but if you've been hanging around El Paso and crossing the border, shoot, that's as tough as anyplace I've been, and most of Mexico too.

I think if it were me, I'd tend to stay more towards the eastern half of Mexico along the coast. Nothing against the west side, but I suspect you'll find water and supplies easier on the east and far fewer desolate stretches.

As far as having a burro along goes, I don't really see a problem with that. They've been used down there for centuries now. They're surely much better suited to that purpose than a horse.

Two mini burros own me and they treat me pretty good. There's a great book you can buy for learning how to care for them and I suspect what it covers would apply to standard burros too. It's appropriately called " Caring for your miniature donkey "

You've already covered what I'd consider the hardest and most important part of what you'll need, and that's learning the language.

This sounds like an awesome trip to me. I'll be sure to follow you online.