This is a great restaurant with the best soy chicken I've ever tasted (lemongrass chicken). The main courses are fresh, healthy and nicely-seasoned and served with a tasty side salad, too. You can pick from a number of stir-fry type dishes, though they also have vegan burgers and sandwiches. My non-vegetarian colleagues were impressed with the food here, too.
The service is amazingly friendly and they also have superb vegan cakes (which are made by an independent baker). The prices at Au Lac are really low (most dishes range $5-8), too, considering the value of the food.
I think Au Lac closes too early, and I wish they accepted credit cards, but it's otherwise highly recommended.