You can vote in person at any of L.A. County's vote centers.  The one in San Dimas is next to City Hall in the Community Building, 245 E. Bonita Avenue.  You can also turn your mail-in ballot here if you have not mailed it yet.

Where to Vote.jpg
Vote Center - Plummer Bldg 2020 a.jpg
Vote Center - Plummer Bldg 2020 b.jpg

More information can be found at LAVote.net.