They have certain days and times for climbing, you'd have to go up there that day and see if you can climb. If not, be sure to check the schedule. Also each day in the daily paper, it will list the times its open.
Hi JD in NJ,
No, there is not a charge for climbing the wall, they will also provide shoes and helmet, just pack some socks. You will have to look in your daily cruise compass for the times when the wall is open for open climbing, it does vary by day.