Its tough to find southern style Indian cuisine in the Portland area. If, like me, you jones for dosas and other southern Indian treats, you can't go wrong with Chennai Masala.
They have an unusually good selection of dosas and uttapam including the standard Masala dosa, and also my favorite, the chole dosa. The chole dosa is a dosa (large Indian rice and mung bean crepe) filled with potato and chickpea curry (chole). The chole dosa is a bit pricey as dosas go, but well worth it.
While not a vegetarian restaurant, they are definitely vegetarian friendly. They have over ten vegetarian curries on the menu in addition to all of the vegetarian dosas, and uttapam. Many of the dishes are vegan, if you ask the waiter, they are friendly and usually aware of what is vegan and what contains cream, butter and cheese. Also, some of the food has fresh green chopped hot pepper, if you don't like your food so spicy, you can ask your waiter to exclude these.
The atmosphere is informal, the prices are fairly reasonable, though not budget, and the are dosas terrific!