Glad you got the message about amps. Use it for restaurant gigs and the like.

Busking IS how you work on nerves, not ahead of time, so suck it up and just go do it :-). Nothing cures nerves like surviving a day (or half-day) of people variously ignoring you, stopping to enjoy your music, and telling you to get lost.

If you truly are very quiet when you play, choose your locations accordingly, perhaps a pedestrian area so there is less car noise (if there is such a spot). Recessed doorways can serve as a natural soundbox to some degree, some are better than others.

Are you often inclined to apologize for your playing? If so, save it for your family and friends, don't share that part of you with your street audience.