Cal. Elections Code - ELEC § 2000. Section 2000.
(a)
Every person who qualifies under Section 2 of Article II of the California Constitution and who complies with this code governing the registration of electors may vote at any election held within the territory within which he or she resides and the election is held.
(b)
Any person who will be at least 18 years of age at the time of the next election is eligible to register and vote at that election.
(c)
Pursuant to Section 2102, any person who is at least 16 years of age and otherwise meets all eligibility requirements to vote is eligible to preregister to vote, but is not eligible to vote until
he or she is 18 years of age.