I went in May 2011.
Really enjoyed it, but yeah it’s humid and wet. Would finish every day with a swim then head back up to my room and get sweaty again. It’s a really cool place though, heaps to do and see plus easy to get around. We were near Farrer Park station (sp?) and found it simple to move place to place.
The zoo is great,
Universal Studios had just opened when we were there and parts of the attractions on Sentosa Island were still being completed. Highly recommend going though.
As for drinking, at least one I remember was outrageously priced. I paid 25-30 bucks for a vodka and lemonade in the Skypark on top of Marina Bay Sands. I didn’t get a second.