If you're in Houston, the Bellaire district has a lot of restaurants. And...
Two great purely vegetarian restaurants:
Quan Yin (extremely good food, HUGE selection of very creative meals like Oysters made of fried eggplant and "fake" meat, affordable prices; great taste!)
and May's Cafe & Ice Cream (good "faster" food place, big selection of tasty hot meals, also has smoothies)

There's also a vegetarian restaurant in downtown Orlando:
Garden Cafe (Colonial SR50 west of I-4) This is a full-serve restaurant, not cafe, and has decent food and good selection but compared to the two spots in Houston, is overpriced.
Also another vegetarian Indian place on OBT in south Orlando, but I haven't been there. I hear it's called "Woodlands" or something like that.

In Boston: In Chinatown I've seen a vegetarian place. Haven't tried it yet, forgot name. In Cambridge, New Asia on Mass Ave isn't a vegetarian only place but does have fake "meat" and a small selection of vege entrees. There's also a good vegetarian cafe inside the Mass Ave Buddhist center between Central Sq and Harvard Sq-no need to be Buddhist to eat there.