Figure out who to call and ask them.
I was a vacationer only. I would love to get back. It is a very nice place. Sorry, I don't know about the fair.
June 9th will be the last day of a 10 day Jazz Festival (May 31 - June 9th). Not sure whether there is a fair as well. https://healdsburgjazzfestival.org/2019-healdsburg-jazz-festival/
Thanks! Your answer is awaiting moderation.