Last night I made these tacos de papa and served them with frijoles de la olla... the recipes came straight out of the May issue of Saveur, whose cover story is the home cooking of the Zacatecas region of Mexico. From Anna's tales of hardship surviving as a vegan in Mexico, I normally expect "authentic" Mexican cooking to be pretty vegetarian unfriendly, since lard (and other pig parts) plus meat based broths are used even to cook something like beans or rice... however there is no reason in principle that the hearty peasant fare of rural Mexico can't be compatible with a vegetarian diet. Now I don't know if Saveur adapted these recipes to be vegetarian, or whether this particular region isn't as fond of the lard (bacon butter!) as others... but regardless, this month's magazine has a couple of pretty unique Mexican vegetarian dishes that you're not likely to encounter at your local burrito joint (in New England at least).
The recipes for tacos de papa (potato tacos) and frijoles de la olla (pinto beans with pico de gallo) can be found here and here. Both recipes are pretty straight forward... and I don't have much to add... except watch it with the salt level in the filling for the potato tacos. The recipe suggest boiling your potato(s) in salted water, but since it also says to peel them... that's going to season them some while they cook (not true if you boil them skin on, which might be a better choice - though skinning hot potatoes is not a lot of fun without a potato ricer). I did not taste the potatoes before adding in the 2 teaspoons of kosher salt and they ended up a little overly salty... so in retrospect, it makes more sense to mash your potatoes, garlic, butter, pepper, and cumin together and then add salt to taste.
Also, you'll need to soften your corn tortillas if they are store bought to have any chance of folding them into tacos. I've had some success with microwaving a stack wrapped in wet paper towels in the past, but this time Anna put them in the microwave with a cup of water and that seemed to work well too.