Since you bring up roadside produce, I'll call out one of my very fave Mexican food experiences: garbanzos. Each year, we drive to a village a short distance from our own where there are several guys on the side of the road peddling bundled garbanzo bushes out of the back of their pickups (dunno why they harvest the whole bush, but they do). My host is very particular about the product, so there's lots of sampling, examining of the plants, sifting through the bushes, etc. We then take the acceptable bushes home, pick off the bean pods and our hostess either steams them or roasts them on a flat pan over a wood fire (the picked-clean bushes get fed to the sheep - nothing gets wasted). The result isn't unlike edamame - you bite the end of the pod and coax the bean out with your teeth. They're crazy good and just writing this makes me miss them. For some reason, I've never encountered anything similar up here.
Interesting to hear your thoughts on the Mexican medical system, trpt2345. Like I said, I was very impressed by what I saw, even if the end result was less than optimal. It was also crazy efficient, which isn't a quality one finds in a lot of Mexican institutions.