I'm currently doing some research. In the UK a person who performs in public places for monetary donations is generally known as a Busker. In the US would they be generally known as Buskers or Street Performers.
I'm in the U.S. I have encountered the term "busker" only in obscure literature. Anyone I have known who has referred to street performers has called them "street performers" (or "street musicians," since that's mostly what we've had in my corner of the U.S.).
I've only heard the word 'busk' or 'busking' as a verb in the U.S., not to describe the actual street performer. So if a person performed on the street with a hat or jar for money, they were 'busking'.
In Australia, we use all of the above terms ie: busking, busker, street performer, street musician etc. Another term, rarely used is "artist"
Here in Philly I've heard both, but I'd say 'street performer' is probably more common. Or something more specific, like 'street drummer' or 'that violin guy at 11th and chestnut'
This is the first time I've heard the term 'busker' and I've lived all over the US. All I've ever heard them referred to as, other than derogatory terms, is 'street performer.'
Many thanks to all of you for replying to my query. As the setting of the story I'm working on is in the US, I'll use the term street performer.