I've been here for dinner a few times, and have always been satisfied but not completely impressed.
There is an entire page in the menu devoted to vegetarian dishes, and other pages had vegetarian options as well. The servers seem to have a general knowledge of veganism and the dishes' ingredients. Alas, neither the naan nor the desserts are vegan. Roti can be ordered in place of naan, and it's on par with the roti at other local Indian restaurants. Many of the dishes contain dairy, but they seem to have some flexibility in preparing them without it.
My favorite Indian restaurant in Tucson is still India Oven. But I felt like I got more for my money at Gandhi: the prices were a bit lower, and each meal included appetizers and side dishes (all of which were vegan except for the raita). Instead of having to pay extra for rice, for example, it was included with our meal.
But despite the value, I found the food to be incredibly bland. The chickpeas and potatoes, for example, hardly seemed to have any seasoning at all. A similar dish at India Oven packs a lot more flavor. Ditto with the dal and the veggie samosas. I've also had the fried okra here, which seemed to be on par with India Oven's counterpart.
When you get right down to it, Gandhi is pretty overrated. I don't understand why it consistently gets accolades from the Tucson Weekly and enjoys the level of popularity it does when there are far superior and more flavorful Indian restaurants just a few miles away.