There are quite a few veggie places here in Santiago.
The adventists have two: one in front of Hospital Cabral y Baez in Los Colegios, and the other on La Restauracion directly in front of Clinica Corominas.
"Oh Light" in Los Jardines is good.
In Las Colinas, on the same street as McDonalds, but a little further up the hill, there is a Chinese veggie place that seems to specialize in fried veggies. Tasty but not very healthy. In Colinas Mall, there is also a veggie place (next to Dominoes)
and behind the Banco Agricola there is a tasty little place called "Naturalis Te" that is kind of Asian Fusion.
There USED to be a Korean restaurant in Santiago, but the owner relocated to Cuba with her family. There is a woman who does Korean barbecue by order (and probably some other dishes as well), but that's neither vegetarian nor a restaurant.