It depends on how much of a scene you make. There are servers who walk around the area asking people if they want a drink.
If you cover the cooler with a pool towel, then hide it under your chair, then no one will see it and you can probably get away with a drink.
If you leave the cooler in plain sight and it's glass bottles, then someone is going to say something. They serve drinks in clear plastic cups. So if you could pour your drink from a beer can into a clear plastic cup, no one would know.
If all else fails, pre game in your room, and buy a drink or two from the servers. They have Heinekin draft.