new member in sf bay area

hey everyone, first post here. well i have been "detecting" since last fall but have actually gone out about 5 times. i've got lots of helpful info from here and i finally joined. btw i have bought used and sold about 4 detectors and finally think i'm keeping the 5th, fisher f4. oh yea most importantly if my younger had'nt pushed me to get into this i wouldn't have started, so hes my detecting buddy. so we have been spending lots of hours researching for places here in the east bay, and when time permits we will go out more.
one quick question, does each city require a permit? or does it vary? i live in hayward. one more, how difficult is it to be granted permission to hunt a historical site? thanks.