Absolutely make a reservation.
When we went in January, we got to the GF about 20 minutes before they started serving for the day and 40 minutes before our ADR. We had no trouble being seated as soon as they were open, but, while we were standing by the podium, the hostess was explaining to a party of 2 that she would take their names and they could wait in the lobby, but there was no guarantee they would be served that day.