I have a house in california but live in illinois? which State real estate law to follow?

For most issues, California law will govern concerning California real estate, including foreclosure. Have you made any effort to work with the lender concerning an alternative to foreclosure, such as a Deed in Lieu of Foreclosure, a short sale, a loan modification that may allow you to keep, perhaps as rental property, . . . If bankruptcy is going to be involved to attempt to obtain a discharge of any deficiency you may incur from the foreclosure and otherwise address any financial concerns, the exemptions that apply will depend on the states in which you have been a resident at certain times and is a complicated matter that will need to be carefully considered by your bankruptcy attorney.