I haven´t tried tejate - my favourite drink in Mexico was Mezcal.

- usually served with slices of orange dipped in "
sal de gusano (Agave Worm Salt). apparently it is very popular in Oaxaca ( pronounced " Wahaca"

) where the Mayan cuisine is very pronounced.
There are some very popular, but rather bland ingredients in Mexico; cactus paddles, for example, or amaranth seeds, or sacred leaves.
as for huitlacoche - not particularly exciting, but ok.
We went to a restaurant in Coyoacán a few weeks ago, and the first thing to appear on the table was a plateful of chapulines (fried grasshoppers), with a hot salsa and some limes. everyone tried them; but to be honest, once you´ve got over the trauma of eating an insect, they didn´t really taste of anything. They were just crispy snacks, like potato crisps. I did draw the line at eating deep-fried scorpions, however.
And yet there are so many exciting dishes: the salsas, the creative use of chiles, the many different
moles, the use of chile/lemon/salt with fresh fruit.
As for cassava, Scullion - there are two distinct varieties: the edible version ( which is gleaming white when cut open) and the venomous variety - slightly pinkish/orangy inside. The latter is really nasty, which is why, when you buy cassava (yuca) here, the seller will always split a root open for you, so you can be sure.