Yes, there is always a women's section, as there is always a men's section also (meaning the sexes are separate). However, a friend of mine has a story of being kicked out from an onsen for her small (5 cm) tattoo of a harmless dolphin on the back of her neck. However, she also said that she had managed to cover it up on several occasions previously, and I guess they don't look THAT carefully at your body. I also suppose when no one complains they don't care. Do you have really big tattoos all over your body?
Oh yes, the hammam... I would love to include that in my series, but unfortunately I don't have a personal experience with that. And those sulfur pools in Tuscany sound wonderful. Actually, I haven't even heard about those at all.