The festival is a giant party for a 10 block length of Fillmore stretching from Jackson Street south to Eddy Street. There were three main stages for music, but also many smaller performances on the sidewalks. There seemed to be plenty of people listening to jazz this last weekend. Maybe jazz has a future and the new Yoshi's Jazz Club and the Fillmore Jazz District is becoming the new hot spot!
The Fillmore has a great tradition and history in 20th Century jazz. All the great jazz performers flocked to the Fillmore when they played San Francisco. See this description for a history of Fillmore jazz.