I've seen the spa upgrade on Orbitz (at the time you purchase your whole trip) to be around 55$ extra per night. This is what we did for our February trip. I have seen the price of the jacuzzi room to be as much as 128$ per night. Here is my advise if you want a jacuzzi room, wait till you get to the resort and upon checking in ask how much to upgrade to a jacuzzi room. If they have some available I've heard it will cost you 50$ extra per night. The only problem is that your going over a time period that I think the resort will be at capacity. See you guys soon!
We just spent the last 5 nights in the jacuzzi room. I think it was worth it since the jacuzzi jets in the pools were way too cold to sit in. I don't think I would do it in the summer, but the cooler winter was worth it.