I've never tried it, but when I didn't have a PS once (I eventually got one) this was the advice I received from the GF concierge. "Show up at a few minutes before opening time, I think they start serving at 5:00. Approach the podium and tell them you wish to be seated, most people have reported that they can get seated in approx 20 - 30 minutes that way. They have to seat everyone with an early PS first, but they NEVER fill the restaurant with those first PS's, so this is your best shot." Good luck and go with the attitude that you might not get in, it has happened before, but this is probably your best bet.