what a coincidence.. i just did my walk in Oakland even though i am from New york. Go to uscis office 5-6 days ahead of your finger print appointment with notice and ask them to do walk in..it depends upon ISO in the office..
If he states he can do walk in same day or ask you to come other day, you should be good. If he says no, try 2 more in area. If no one agrees go to your state.
Oakland ISO was nice. I went there thursday and he asked me to come back today. Just came back from my biometric in oakland even though i am from NY