San Francisco is always a celebration — and this is just a taste of what one weekend day can bring.  Blues, kazoos, artful dance, rising musicians, even an event that brings out 400,000 to showcase leather-clad accessories — it’s all a brilliant blend of all that makes the city shine.  This day brought me to the very first Polk Street Blues Festival, the 27th Folsom Street Fair, the 8th annual Cole Valley Fair, and the first annual Central Market Arts Festival.  All these artists rock and I am completely mesmerized by the tunes of Kate Kilbane singing Sweet Unknown.