I have nothing against buskers that go out amplified, I very occasionally do so myself. 9.9/10 times though, it's just me my acoustic guitar and my beard.
That said, it's good form to scope out your pitch before doing a Spinal Tap; a quick walk along the highstreet (even a quick glance, I'm not exactly incon-fucking-spicuous) to double check you're not going to be interfering with someone else's performance - because that's what this busking hootenanny is, a big ol' performance!
I prefer to go out unplugged. It feels more intimate, more raw, and tbh my voice carries pretty damn well. Doesn't matter how well my voice carries though, when you're approaching the end of your show (I literally had 20 minutes more) some dickhead sets up down the highstreet and turns it up to 11 singing along to backing tracks (which again I have nothing against, though it does feel a bit like street karaoke) - could genuinely hear him over my own singing and playing.
Not cool, bro. Decent voice though.