Used them and there are multiple machines. Also there are 2-3 facilities in the GCH. They are tricky to find and require some navigation (at least for me).
They weren't cheap, I seem to think it was like $1.50-$2 each. The token machine was beoken during my visit too and I had to get them at the feont desk. So, id recommend getting tokens & directions so you dont have to trek back. Also, there are times that the dryers are full even if the washers aren't. I guess people use the dryers after repeat GRR rides and/or to dry bathing suits. This might not be a common occurrence as I only have used the facility once during our one trip. However, I thought I'd mention it.