Strange. You are a newbie but yet you have chosen to go to a place, Yunomori Onsen, as your absolutely first choice? A place that seemes to be for both men and women according to the little information I can find on the Internet about this place that I had never heard about before.
And you have read about it on the forum you say? By searching the three main gay Thailand-forums I can not find that this place has ever been mentioned there. Please add link to the forums with more information on this place.
I must agree with Kokopelli that maybe it is best for you to avoid this experiment of yours and stick to the Internet.