i went to plantation last year...i swear it was the best week of my life!!
and as for money it really depends how much you drink. activities aren't TOO expensive and most people didn't spend much on them. drinks are pretty cheap too, especially if you walk around to the next resort - musket cove. the drinks there cost about the eqivilant of AUD$3 or so. i think i spent about $600 all up. probably a bit less actually. but be careful with the cash that you take because a lot of people had money stolen from them. it's actually quite convenient to just take a credit card and charge your drinks to your room - and don't worry you don't have to try and split the cost with your roommates, they have it all itemised on the computer under your name