They are taking walk-ins but you would have to be there early in the morning to get a good spot in line, I made my appointment a month in advance so I had time to study. All about preferences
If you walk in, you need to be there well before opening. A couple of hours at least. They are only taking a specific number of people each day. Appointments on the other hand must be made well in advance. A month if you are lucky. But, you will not have to wait long once you arrive.
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