I recently spent some time in Montanita and could not find the other 2 veggie restaurants listed here. It doesn't help that there are no street names in the town. However, you can walk them all fairly quickly. I did come across this place which has a vegetarian menu but then has a few fish dishes on the board (go figure!). There is a separate breakfast menu, and the a lunch/dinner menu. I had the burritos twice without cheese. This was very tasty and came with a fresh salad on the side. I had this twice and recommend it.
Cons: More vegan dishes would be good