I dunno really. The vegetarian situation is different in teh US than it is in the UK. In the UK, if you leave the vegetarians out, then you're f**ked, so almost every restaurant will take tiem to consider vegetarians, as you're obviously going to get them.
But I think that taco bell might be aware of vegetarians. If they become more aware, tehn they might start to develop the menu to accomodate vegetarians even more. You never know. But it would be a good idea to be positivce and upbeat about taco bell. From the sound of it, American fast food restaurants tend to be very veg-unfriendly, and taco bell seems to be an exception.