There were quite a few. We were really lucky and ended up in a group of 4 and had quite a personal tour. The group behind us were about a group of 10. Just had to be patient and wait until they passed. Thnaks very much!
Yeah you are not allowed to visit on your own due to flash floods. Im not sure about night viewings... Not sure how much you would get from seeing it at night... maybe under a full moon (you could probably go down and see it for yourself at night, its not fenced off)