Not sure about the US, but in Oz we were instructed during the brief to tell them to only do so (window/self help exit) if they hear the command 'evacuate evacuate' and there is NOT an FA in the vicinity of the exits...
I always used to tell them what I wanted them to do if the exit was blocked/after exiting eg 'do not open the exit and do not let anyone else open unless it is safe' 'once you exit help the others away from the aircraft and upwind'
Ok maybe it was a bit more than required but it made me feel more comfortable and a number of them always commented 'I always wondered what you were supposed to do afterwards'