Legal Question in Landlord & Tenant Law in California

You don't do anything differently. You are legally obligated to continue your tenancy by its terms, including payment of rent, unless and until you are notified of an actual foreclosure sale. After the sale you must "attourn" to the new owner, meaning you continue your tenancy complying with the exact same terms and conditions as if the new owner had been your landlord all along. After the sale, as long as you pay your rent and comply with your other obligations, you are entitled to at least 90-days notice if they decide they want to terminate your tenancy under a month-to-month rental. If you have a lease that will not expire for more than 90 days, they have to let you stay until at least the end of the lease term. So if it sells you are actually slightly better off than if you keep the original land-lord, because they only have to give 60-days notice under a month to month.