I guess that's the problem with performing at an event where there's so much going on. People may just assume you've been booked by the organisers for their enterntainment. And will have consumed too much real ale or cider to read your sign.

Years ago when I lived in Girona, there was a Romanian accordionist who would busk the streets and squares. One time a friend of mine was visiting, in the week when he was also trying to finalise a problematic house purchase which was dragging on. We sat down for a drink outside a bar when he got a call from his solicitor, just as the accordionist turned up alongside. He couldn't hear a word the guy was saying, and gave the busker a very generous contribution to encourage him to wander off elsewhere.

Maybe that's the solution: accordion-playing with menaces. Seek out couples about to make marriage proposals, that kind of thing, park yourself next to them and take the hush money.