Mexican restaurants are usually a suspect for vegan options, but On The Border delivered. My wife and I both had the portabello mushroom and vegetable fajitas with white corn tortillas (these are the only veg friendly wraps available).
The guacamole was pretty good and dairy-free. We asked for no cheese with the fajitas, but it came with cheese on the side. The staff was quick to give us a new plate of lettuce, salsa and guacamole without the cheese. The corn tortillas were made fresh for us (although the first set sent to our table were the wheat tortillas). The black beans were spicy and not bland like I've had at other restaurants. All in all, the spicy level was higher than most Mexican joints and more to my liking.
The staff was very helpful and even comp'ed us our meal since the kitchen messed up on the cheese and tortillas. We didn't even ask them to do this, however the manager wanted to make sure our dietary requirements were met. Five of five stars on helpfulness!