If you believe you are disabled and are unable to work you should apply for Social Security Disability benefits right away. In fact, you can apply for SSDI benefits at the same time you apply for California State Disability Insurance (SDI). The process for obtaining Social Security Disability benefits can take a long time, especially if you are denied once, twice or more times! Social Security estimates that it takes 90 - 120 days to process an initial application. However, the wait can be longer. For someone who must wait until the Administrative Law Judge (ALJ) hearing to be awarded benefits, the wait time from the initial application to ALJ decision can easily be two years!
If you cannot apply for benefits right away but know that you plan on filing you can contact Social Security to get a "protective filing date". Essentially this means that you have notified Social Security that you intend to file for benefits within the next few weeks or months. This becomes your application date. An earlier date can make a difference in the amount of back pay you are owed. For more information see Protective Filing Date.