Best Vegetarian Downtown?
One of my favorites is the Sultan's Kitchen on State St. They have a wide selection of fantastic veggie dishes like stuffed eggplant, artichoke fritters, bean salads and such. They are open until 8:30pm so you could do it for dinner. It's a tiny place, but there are a few tables, and it's not crowded except around lunch time when it's packed.
In the South End, I like Thai Village on Tremont St. They have plenty of veggie dishes on the menu. Another great choice is Addis Red Sea Ethiopian, which has plenty of vegetarian choices as well.