And you cannot until you arrive. And as @wild1s advised they are only needed for She and id sitting at the Hibachi grill at Sutra. If you just want to sit at a table then no reservations are needed as you can just walk in. May have to wait at bar a bit if crowded though.
We found that waiting at bar to be seated is a great place to meet new people and then ask to be seated together...great way to make new friends over nice dinner.