I agree with earlier poster. San Angel is noisy and the food isn't good. The River is nice, but rarely will you get to sit right by it. We've found that eating at the Cantina de San Angel is much nicer. The food is better and you can sit on the water and enjoy the view of the Epcot ball and all the countries.
I know San Angel Inn is noisy, crowded, tables jammed right up next to each other, has pretty poor service and the food is fair, at best. They also have the wrong kind of Dos Equis on draft (light--not the amber).
It possibly might be OK if there were just two of you and you got a table right next to the River of Time.