I actually like Cantina de San Angel far better than the restaurant inside. The food is good, reasonably priced, and it's kind of nice sitting by the lagoon (if there aren't too many birds, that is!)
We also liked it, and we must not have a very good Taco Bell because the Cantina was a lot better. The servings are huge, so it if very possible to share. Yes, be warned about the birds!!
There are tables - all outside - where you can sit near the water. They get filled up when Illuminations is drawing near.
It is a lot different than Taco Bell. My son who eats Taco Bell all the time took one look at his black beans and wouldn't touch any of his food there (which is fine, he can starve if he chooses). If you and your kids like mexican, it's great.