I went to try and do a walk in yesterday morning at the Phoenix USCIS and the guard told me that they only allow walk ins after your appointment date and not before. It's so lame though since so many walk-ins have been allowed in other states. I hate living in Arizona and can't wait to get out of here. But at least it's a good thing for those people that for some reason missed their appointment date like you. Good luck!
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Lawyer?: Screw that! Filed by myself
Application sent: 8/24/12 from Phoenix, AZ
Application arrived: 8/25/12 10:37 a.m.
Application rcvd G-1145 & I-797: 8/29/12 9:27AM fwd to CA Center
Bio received: 9/10/12
Appt:9/26/12 @ 10 am
EAD: Approved!!! 3/22/13 - 6 months and 25 days of waiting.