I went to the Dallas office (Whitehurst Dr) twice, both time on the same day of my appointment, but was there way earlier than my scheduled time. The lady at the front that gives you a form to fill doesn't really look at the date and time on the notice (she does verify your name on the notice though) and gives you a form to fill as there is a line (about 20-30 people), so they try to do everything as quickly as possible and keep the line short.

I would give it a try (I went early in the day, around 10). The workers at this office are nice, so thats goo d as well.