There are a bunch in Los Angeles County. Here is the current pdf from SafetyBeltSafe with the centers all listed with drop off times/locations/days and contact numbers.
http://carseat.org/Recycling%20locations.pdf
And my attempt to paste the text:
TMC Horizon Inc.
1315 East 4th Street, Pomona
91766. 562/692-2700
Drop off Monday through Friday, 9 a.m. to 5 p.m.
The Children’s Collective Inc.
255 East 28th
Street, Los Angeles 90011.
213/747-4046
Call to schedule a drop-off.
Children's Hospital Los Angeles, Injury Prevention Program
4650 Sunset Blvd., Los Angeles 90027. 323/361-4697
Drop off main entrance, 1st Friday of each month, 8 a.m.-5 p.m.
Miller Children's Hospital, Long Beach Family Resource Center
2801 Atlantic Avenue, Long Beach 90806. 562/933-9151
Drop off on Mondays and Wednesdays,
Long Beach Blvd. entrance, 1 p.m. to 3 p.m. OR call to schedule a drop
-off in driveway OR park in structure (free for 30 minutes) and go to 2nd floor.
Belmont Kidz
2734 E. Broadway, Long Beach 90803. 562/433-9151 (contact: Maggie)
www.belmontkidz.com www.facebook.com/belmontkidz
Kids Double Time
715 Torrance Blvd., Redondo Beach 90277. 310/542-4407
Monday-Saturday, 10 a.m. to 5 p.m. Sunday, 11 a.m. to 5 p.m.
Kidz Head 2 Toe Children's Resale Boutique
5467 E. Carson Street, Long Beach 90808. 562/627-5438 (contact: Christina)
www.kidzhead2toe.com www.facebook.com/KIDZH2T
New Economics for Women
201 North Beacon Street, San Pedro 90731. 310/519-8221
Drop-off location next to parking garage entrance on Beacon Street; call to schedule a drop-off.
New Economics for Women
7500 Alabama Avenue, Canoga Park
91303. 818/887-3877
Entrance at corner of Saticoy and Alabama-Purple Building. Call to schedule drop-off