It's supposed to rain on Sunday, but that won't stop the Sunday Streets and the two-weekend long Cherry Blossom Festival fun. Also happening on Sunday is the Festival of the Mandolins, which has a huge line-up.
Saturday includes the Cesar E. Chavez Holiday Parade & Festival in the Mission and the International Lao New Year Festival at Civic Center.
The Inner Sunset neighborhood is having a Free Book Blast (via Funcheap, N Judah Chronicles), and Golden Gate Heights plays host to the URBIA SF Treasure Hunt No. 1: Islands in the Sky (also via Funcheap).
For something completely retro-different, there's the Booze, Broads, and Hotrods #12 rockabilly festival in Millbrae.