Great ride report! Read it, then went back again and read some more, though I never did get why you decided to return when you did. With a no-plan kinda plan, those factors that influenced you while on the road would be good to know. If I just missed it and it's very clear, my apologies.
But what I'd also like to know is, and I don't mean this in a critical way at all - didn't you miss not being able to truly speak to the locals, meanwhile you don't speak Spanish? I spent two weeks in Mexico City two years ago and spent three of those days exploring the mountains north and east by car. I really missed not being able to ask much more than where the bathroom is (though that can be damn important!).
I ask you this because I'm planning to head south as early as next October, and one of the things holding me back is my lack of Spanish. I will probably take one or all of the Rosetta Stone courses, but I'm getting on in years (30-yr HS reunion coming up in Orinda next fall), was never very good at learning language, and don't know how much I'll be able to learn before heading out. So that's why your answer, as to how it was getting around and how much you think you might have missed out on is important to me.
In any event, great ride report and thanks for sharing!