My ex husband and I, both 66 and my mother 91 would like to drive from NM to Costa Rica. We are all in good health. We also have a dog. Are we crazy?

Please don't. Unsafe for several reasons.

I'm not convinced this a serious post.

How hard is it to bring a dog to CR? My ex has a boxer. That's why we were considering driving.

Are you moving there or planning to visit as tourists?

Driving through Mexico is just a bad idea. Bad, dangerous idea. And if you get through Mexico without getting carjacked, there's still places like Guatemala and El Salvador and Honduras to get through.

Technically, to cross the Mexican border with a pet, you need to have a health certificate signed and dated within 3 days of your arrival. Although the reality is they rarely check. Costa Rica has similar requirements: http://costarica.usembassy.gov/catsdogs.html
I'd suspect the other countries do something similar.
With all due respect, this is just a bad, bad, idea on so many levels.
Give your dog a pill and put it on a plane.

And as long as you're apparently not willing to do your own research:
http://nicaragua.usembassy.gov/bring...nicaragua.html
http://guatemala.usembassy.gov/uploa...g/acsepets.pdf
http://www.pettravel.com/immigration/ElSalvador.cfm
Otherwise, you run the risk of having your dog quarantined in each country you enter.