i've planted fava beans, now about a foot high....never planted these before, don't know anyone who has...

do i need to cage these, or will they support themselves as the stems mature? right now they are flopping over at the least provocation (morning dew, light mist, etc)

You need to look at the packaging of your beans to see if they are a bush variety or pole variety. That will tell you if you need to cage them. Bush varieties do not need cages normally.