Pho Dat Thanh doesn't strike me as the most authentic Vietnamese restaurant (the menu contained several dishes that I tend to order at Thai and Chinese restaurants) but I was grateful for the fact that the menu was so friendly to vegetarians. The waiter mentioned that all dishes containing fish sauce are labeled as such, so vegetarians don't have to worry when ordering food here.
I ate at Pho Dat Thanh for lunch and the portion was huge - easily 3 meals' worth of food for a very reasonable price. The menu had a good selection of bubble tea flavors, but it's important to ask which flavors contain milk if you're vegan (unfortunately, that aspect of the menu is not clearly labeled). I ordered the tofu in brown sauce, which came on a bed of vegetables and rice noodles. The sauce was pretty tasty, but the whole dish was a bit greasier than I would have liked. Overall, I thought that this was a decent quick food option in Towson, especially for the price.