Hi, Nancy! Chef Mickey can be a tough reservation to get your hands on, and many people call in at the crack of dawn on the first day they can when their 180 day dining reservation window opens to get the reservation they want! That doesn't mean, however, you are totally out of luck.
If you have a specific day or time in mind, keep checking through the website. In my opinion, however, I think calling to see if there has been a cancellation has resulted in much greater success. There are always cancellations - especially as the time draws closer and people firm up where they want to be on which days. I would say at least right now, call every couple of days to see if something might have opened up, but as you get closer, call every day.
If you get all the way to your vacation and haven't secured a reservation, there MAY be a chance you could get a table by walking up. I know guests who have tried in desperation to secure a reservation, and when they haven't succeeded, they go as soon as the restaurant opens to see if there is any chance of a last minute table. It works sometimes, sometimes it doesn't; so keep a back up plan ready just in case.
I'm sending you some virtual pixie dust in hopes that you get a table!
Have a great vacation!