Alright, this summer my family is going to Mexico, and we always go by car (in a truck). I'm going to be going by car from Texas to Mexico, and I want to take my Norfolk pine tree with me. But I don't know how to take it with me and make sure it's safe on the way, because the trip to Mexico from Texas is a day long.
Your plant may be safe to travel in a truck but it may be be allowed and you may have to leave it before you can enter Mexico.
I found this website helpful, www.bajabound.com/
It states, Regulated imports may be brought into Mexico according to their origin and manufacturing process and they have fulfilled the importation requirements.
I suggest contacting www.gob.mx/
so yes, checking the legality of transferring flora across country lines is very important - it wuld be terrible to get stopped in customs over a pine tree, they miht even get it into their heads that you are actually importing/exporting worse contraband and it might not go well with you
so saying, if you know you can take it with no problems legally, then it should do OK in a pot with lots of water. Tie it down or even wrap it with twine the way they do with Christmas trees when you buy them off the lot (image) and then tie it with bungee cords to the bed of the truck.