What are tenant's rights under CA landlord tenant act for being evicted due to landlord's foreclosure

If you are still under a lease that has not yet expired, then you can fight the eviction. If you are on a month-to-month then you are going to have to move.

I am not licensed in California so my answer cannot be specific to your state. In Florida and most other jurisdictions that I am aware of the lien of the mortgage that is being foreclosed is superior to the lease that you signed because your lease is not recorded in the public records. The mortgage holder has the right to foreclose out whatever rights you have under the lease and usually names the tenant in the foreclosure as a John Doe or unknown tenant. They must serve you with a summons in the foreclosure to cancel your lease. If they do not you become the tenant of whoever buys the property as the foreclosure sale. California may have a law that protects tenants in the case of foreclosure so you should consult with a California licensed attorney. You can usually check with your local county bar association for a low cost consultation.