I can't see how your supposed to do fiesta forever without the bots killing each other, Their weapon arsenal is insane like I got nuked twice in a game. If only the bots also only use pinata's, or if there was only 1 bot or if they get lower hp is the only way this mission would work. I know it's supposed to be one of the hard missions but this is just ridiculous.
For some reason I was able to do it first try without much difficulty. I cannot help you but to tell you to keep trying!