I showed up last time (2 weeks ago) to check it out. They had some streets closed in the financial district/China town area, but it was really silly because they were closed off in 1 block sections, so you had to stop every block until the traffic control officers stopped tracffic. It was great for the local little kids though whi just went up and down the block.
The section along the Embarcadero from the Ferry Building heading South toward AT&T Park was much better since it was all closed off. It was crowded though, which is great to see, but makes it difficult if you want to cruise along at 20mph+. It was much less crowded south of the Park & piers along Terry Francois/China Basin.
So, I wouldn't go solely for riding back and forth along these streets, but would likely plan my Sunday ride to pass through the closed streets area.