We usually figure $100 US per day, per person. Most days we don't spend the entire amount, but I would rather make sure I have enough budgeted per day to make sure I have as much fun as possible, rather than feel strained while on vacation. I think that our daily plans pretty much match what you described. Sunnyside is probably about the cheapest for RS ($160J). Yellow Bird has awesome all day happy hour specials until 6:00, I believe. 2 for 1 drinks (5 choices) for $500J if I remember correctly, and $200J RS. White Sands also has a daily 2 for 1 happy hour(1 choice). I haven't been there in low season so you might find even better deals, but I can't imagine it being much cheaper. Hope that helps!!
