I spent two years living in Thu Dau Mot, and this is the best veggie place in town. It's run by a very friendly family (the men sometimes wander round topless with pet roosters under their arms, but don't let that disturb you).
The staff can muster just about enough English to assist if you don't speak Vietnamese, and some of the menu is in English, in case you're not comfortable with pointing and hoping. The seaweed soup and pho are both highly recommended.
Cons: Basic decor, Limited English