The parrots follow the fruiting of the trees, but try Upper Fort Mason, near the Golden Gate National Recreation Area headquarters and Telegraph Hill.More information here:http://www.wildparrotsbook.com/parrot_pa��http://california-travel.suite101.com/ar��
There are several flocks in the city. The one place I can tell you that will guarantee you being able to see them is the Green area just north of Embarcadero Center 3 at about 6pm any night. They go there because there are people who feed them at that time.But as you wander the city if you hear them squawking look up. They are hard to miss.
Just walk around North Beach and head up to Coit Tower on Telegraph Hill, you ll hear them first =)
the zoo.. Oakland have some , not sure about SF
i don t know but i gave you a star, i have a contact who lives there, i know best place to see seagulls is Alcatraz