I don't think Michael was acting recklessly in Cuba. He operated with the confidence and assurance that he knew Roth was behind the Tahoe shooting, and that Roth wanted him in Cuba so he could be killed. He also was confident that Roth still thought Michael believed that Pentangeli was behind the shooting and that their relationship was still good. A classic example of the Corleones' craft of making your enemies relax and get careless by thinking you're weak or stupid.

Michael, like every American who read newspapers in '58, knew Batista was governing on borrowed time. He couldn't have known when Batista would resign. But, I think he was being ultra-careful by going, very visibly, to the Presidential party while Bussetta was attempting to kill Roth. He ordered the plane so he could get out of Cuba fast, before the authorities could start rounding up suspects in Roth's death. Even though Bussetta tried to smother Roth so it might look like a natural death, Batista and whoever else was in on the plot against Michael would have linked him to Roth's death--and in a dictatorship, they don't need warrants and court orders to round up suspects.