I would have said No. I'd never marry anyone who made me publicly humiliate myself like that and was cruel enough to make me believe he'd forgotten our anniversary. He deserved having dinner with a pissy boyfriend and being shouted at. He could have suggested they celebrate it in the same place of their first date and kept the chocolate cake and the proposal as a wonderful surprise.
On the other hand, why does his boyfriend have to be the one to set up this - it makes the teller seem like a passive (dare I say girly) person rather than a man. He could have invited his boyfriend out and avoided all the silly pouting and feeling put upon. But since they love each other, and both seems to enjoy the joke after the act, I guess they're made for each other. For my part, I liked the cool waiter best.
Rant over - I enjoyed that. Hope you don't mind.