I would say mid morning to afternoon. Also, Mondays, Fridays, and the day after holidays are very busy, as well as first of month when a lot of people get paychecks. Better to make an appointment unless you can't wait. I retired from DMV 12 years ago and now operate a driving school, G & G Driving School, LLC in which I take students there several times a month for the driving test.
Its busy all day. I'd recommend going before they open and wait in line so you'll be done by lunch time.
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