TB - good luck! There was one last week here in Dallas but I'm still nursing an IT band injury. I will say stairs are the one form of cardio that kicks my ass...always a good workout.
I like brikis' comment on the bleachers - I'd say it's more for sprint/interval type workouts where you can fly up, brief rest, repeat. It is a hell of a workout though, I do it during speed season/when I'm not training for races in particular. If you're looking to do 80 flights at once, you're probably better off being able to simulate climbing stairs at a slower pace for the same number of floors. Just my opinion though 🙂