Three points:

1) You can't sing well if you're yelling all the songs.

2) People under 50 or so have been listening to loud amplified music their whole lives, and most of them haven't the slightest concept of shutting up and listening, and letting other people listen. They expect to talk - not whisper, talk loudly - while the music's going on, and to be able to hear it over their own conversation. God damn them all for selfish slobs, but that's the way it is.

3) A guitar "plugged in" never sounds as good as a guitar played into a decent quality mic. Many manufacturers of acoustic guitar pickups claim they can produce a true acoustic sound. They are liars. If the room is really noisy, though, it probably doesn't matter.

In terms of sound quality, an unamplified guitar is best, playing into a good PA through a good mic is second best, a pzieo pickup is next, and a magnetic pickup is worst. In terms of being heard in an large, noisy, acousticly bad room, the above order would be exactly reversed.

Peter.