You are right, right now your house has no value:
The Value will be determined when the Bank re-sells the house.
The DIFFERENCE between that Sales Price, and your LOAN AMOUNT will determine the DEFICIENCY.
Also, your clock will not start until the Escrow Closes this next sale.
I have that on good authority that the Banks will use the re-sale date for your 3 years of penance.
Now, the good news;
California is a Non-Recourse State:
There are some restrictions, but you be Okay with regards to a Deficiency Judgement. Those exceptions could get you; so I suggest you read up on California Deficiency Judgements.
At least the IRS is considerate about the whole thing: Look at the Debt Forgiveness Act of 2009.
Good luck and may God bless