www.vitalrec.com leads you to the address for any county in CA to order death cert. You can write yourself to the court address or use them (a little faster and a little more expensive).
go to site, click on states/territories...click California......choose your county.That should give you the exact address and sometimes the fees/info involved to obtain death cert.
What is nice about death certs is that you don't usually have to showproof of next of kin.The county record of death is usually available, where sometimes, the state didn't get the record from the county.
As for death records in 1968...you can go to www.yahoo.com and click on newspapers....but those are only current newspapers.Your best bet is to find the Imperial County Public Library on the internet and ask them to help you with obit.