I have a BlueBird. If there is more clearance it's not but a couple inches. Although I can't really say for sure. I can't even go out an measure since we are in TX & the bus is in NM. Ours is 40 ft long and it came out of the mountains of NC. That means some really steep driveways & roads off a flat road. There is no damage under our bus that looks like it dragged or anything. And it was used to ferry river rafters to and from the river. I do know that the steps at the door are 24" below the bottom of the floor (side panels are not that low... 18" maybe).
As for traveling in Mexico, try asking that question over at http://www.escapees.com
discussion forums. There are a lot of folks who spend a great deal of time south of the border. I do know that you have to have special Mexican insurance that you have to buy thru Mexican insurance companies. They are saying the area close to the border is dangerous but farther away it gets safer. I don't keep up with those threads. I have no grand desire to go Mexico. I don't care for the food, we don't speak the language (so we're bound to get into trouble) and based on the Mexicans here in Corpus... they are very bigoted against non-Mexicans (also ran into that in NC).But then I also have no desire to see France, Italy or any of those other "must see" countries. Now Scotland, Australia/New Zealand and Germany (much less so) are the only foreign countries that I would want to see. My first goal is to see more of the US. It's such a big country and we have seen so little of it (one day I want to make it up to Alaska to do the "top of the world" drive). I would rather go to Canada. We watched CBC on our C-Band sat dish and saw so much of Canada on TV that we would like to see it up close and personal.. and for more than the few hours we spent at Niagara Falls. But that's us.