I do remember doing my first gigs with a spanish guitar and no PA to rooms of up to 100 people! I think mics do help maintain the voice if the singer works regularly. The problems come with the man on the desk and the sound level. I think you have to be very firm as to how loud you want to be and the voice should always dominate the instrument for songs.
I prefer to wear the veil when I post sometimes,hope you don't mind.