Most likely, you would be charged with criminal trespass.
Unless you will be paying the property taxes on this property for the next 5 years, you might as well forget about adverse possession. The elements necessary to establish ownership of real property by adverse possession in California are as follows: “(1) the payment of taxes, (2) actual possession which is (3) open and notorious, (4) continuous and uninterrupted for five years, (5) hostile and adverse to the true owner's title, and (6) under either color of title or claim of right.” (California Maryland Funding, Inc. v. Lowe (1995) 37 Cal.App.4th 1798, 1803.)
The information presented here is general in nature and is not intended, nor should be construed, as legal advice. This posting does not create any attorney-client relationship with the author (who is only admitted to practice law in the State of California). For specific advice about your particular situation, consult your own attorney.
The bank does have people check on their properties on a regular basis so pretty soon they will know you are there and commence legal action to remove you from the property. I agree with the prior answer as well, but the bank will not allow you to stay that long anyway.
The author of this posting is licensed to practice law in the State of Connecticut. This posting is intended as general information only, and is not provided as legal advice in connection with any specific case, and does not create an attorney-client relationship.