Traveling with a small dog

Best I know, the major 1st class bus lines do not allow pets in the passenger area, they must be stowed in the luggage area. Ugh.

Ugh is right. That is completely unacceptable.

You probably can take a dog on one of the second class busses. It's been a while since I've been on one in Mexico, and it was an old Greyhound, not quite as funky as a chicken bus in Guatemala but more comfortable. One of the more bus inclined regulars here will know more.

You actually can, but the conditions are a bit tricky and differ from company to company. I did see a woman with a dog in a bag last month on a Futura.

http://patadeperro.paulaithurbide.com/viajar-con-perros/viajar-con-perros-en-autobus-en-mexico/

https://www.ado.com.mx/ado2/terminosycondiciones/

Those links specify that animals must be transported in the luggage bay, must be sedated, trips of 8 hours or less, and only when temps are under 30c. Only seeing eye and rescue dogs permitted in the passenger area.

Sort of... it's different for each line (Chihuahuenses doesn't even allow seeing eye dogs on board, but ETN is apparently more tolerant). There are also accounts of people who traveled with small dogs in bags... just like I saw on Futura – which is actually ETN – last month. It was quiet and just hung out, and nobody said anything.

"Yo viajé desde Distrito Federal, hasta Tabasco en ADO con un perro pequeño en el maletero..."

https://mx.answers.yahoo.com/question/index?qid=20130313223513AAh8YGA

Bottom line is that it's sometimes possible and there are Mexican exceptions to the "rules," but it does sound like a pain in the neck.

Get a certificate made up, that the dog is a service dog. It will be allowed more places with this, for instance some beaches only allow service dogs.

The dog in that link was still in the luggage bay. That's no exception. Must not be too uncomfortable however, if the relief driver slept there too.

I had a seatmate once who hid her small dog in a blanket and carried it on board a Boqueron-mark bus, that trip was between Putla Villa de Guerrero and Huajuapan de Leon, so several hours.