You can't cup your ear if you play an instrument to accompany yourself.

As a singer who rarely uses PA, when I do I find the fold-back quite off-putting, and prefer it turned quite low. If I can I won't use fold-back at all. I'll have the speakers set in a position so that I can hear them too, without causing feed-back. Keep it simple, even in a folk-rock band.

But I do agree with a previous suggestion. If going acoustic, listen to other singers from the back of the room. Judge how much effort they are putting in. If they can be heard alright, then you will be too, no matter how 'dead' the room seems to be from the front.

Tone (not tone deaf, yet)