The office at 5600 Overland Ave. will be open from 8 a.m. to 5 p.m. Saturday and Sunday.
"Long lines may be an issue on Election Day as voters fill out the longer, two-card ballot," said Registrar of Voters Michael Vu. "Weekend voting gives voters yet another option to cast their ballots or drop off their mail ballots before Election Day."
The office will also accept voters on Monday during regular business hours and on Election Day while the polls are open until 8 p.m.
For those who have completed their mail ballots, they can drop them off at the registrar's office or one of numerous locations around the county during their regular business hours.
The drop-off locations include libraries in:
-- San Diego, North Park Library, 3795 31st St.;
-- San Diego, Pacific Beach Library, 4275 Cass St.;
-- San Diego, Scripps Miramar Ranch Library, 10301 Scripps Lake Drive;
-- San Diego, Valencia Park/Malcolm X Library, 5148 Market St.;
-- Carlsbad, 1775 Dove Lane;
-- Chula Vista, Civic Center Library, 365 F St.;
-- Chula Vista, Otay Ranch Library, 2015 Birch Road;
-- Coronado, 640 Orange Ave.;
-- El Cajon, 201 E. Douglas Ave.;
-- Encinitas, 540 Cornish Drive;
-- Escondido, 239 S. Kalmia St.;
-- Fallbrook, 124 S. Mission Road;
-- 4S Ranch, 10433 Reserve Drive;
-- Imperial Beach, 847 Encina Ave.;
-- La Mesa, 8074 Allison Ave.;
-- Poway, 13137 Poway Road;
-- Ramona, 1275 Main St.;
-- Santee, 9225 Carlton Hills Blvd.;
-- San Marcos, 2 Civic Center Drive;
-- Solana Beach, 157 Stevens Ave.;
-- Spring Valley, 836 Kempton St.; and
-- Vista, 700 Eucalyptus Ave.
County elections officials remind voters that not all libraries are drop- off locations.
Ballots can also be dropped off at the Carlsbad Alga Norte Community Park, 6565 Alicante Road, and the Oceanside Civic Center, 300 N. Coast Highway.