yes they accept walk in, when i applied for my passport i had an appointment at the SF passport agency, i went in the morning and i was waiting in the line, and the guy who was behind me in the line did not have any appointment, he was afraid they are not going to let him enter without appointment, when we reach the door, the officer asked him about appointment, he told the officer he has no appointment, the officer allowed him to go inside, i saw him inside applying for passport, they told him to come after noon and pick up his passport because he was suppose to fly next day