Crouching/Proning only works if you're on even or lower ground than the betty. I've seen one and walked up stairs heard the "VRRRPPP" of it and crouched, then BAM! Dead. sh*t pisses me the fu*k off. If I crouch, I should be immune to that bull sh*t!!! I can't live if I'm rushing around constantly? I'm getting k!lled by a bouncing betty that doesn't actually even bounce but just makes a really high pitched fart noise and k!lls me? Bull sh*t...
Well the thing is if they put it on the stairs, you'll be at the level of the blast when you go up the stairs, so you're going to die regardless. Get flakjacket and you won't have to worry about them ever again.
The stair tactic is the best possible place to put them though.