If you get there right when they open for lunch and ask, there is a chance. I've seen people walk up and get in at that point before. I've also been there when one group has walked up and gotten in and then a couple of minutes later a 2nd group walked up and was told nothing was available the rest of the day. You never know. If they tell you no, the minute it opens, I would probably wait 30 minutes or 45 minutes and ask again, just in case something were to happen to open up. I wouldn't get my hopes up though- it will take a bit of luck!