California - Vote by Mail AND Come on Down!
https://www.sos.ca.gov/elections/voting-resources/voting-california/if-you-applied/
Voting at a Polling Place after Applying to Vote by Mail
Even if you receive your vote-by-mail ballot, you can change your mind and vote at a polling place on Election Day. To do so, you can:
Mark your ballot and seal it inside the mailing envelope provided by your county elections official. Be sure to sign and date the outside of the envelope in the space provided. Then bring the sealed envelope to any polling place in your county, or to your county elections office between 7:00 a.m. and 8:00 p.m. on Election Day.
OR
Bring your unused vote-by-mail ballot to your local polling place anytime between 7:00 a.m. and 8:00 p.m. on Election Day and give it to a poll worker, who will exchange it for a polling place ballot you can use instead.
If you do not bring your vote-by-mail ballot with you, you will not lose your opportunity to vote at a polling place on Election Day. A poll worker will provide you with a provisional ballot, which will be counted after your county elections official has confirmed you are registered to vote in that county and did not vote more than once in that election.
UNBELIEVABLE! They even provide instructions on how to cheat the system.