Brent Simmons of NewNewsWire fame has a fine blog posting full of information for WWDC first timers. I'm not a coffee drinker, so can't really comment on his statements with regard to that particular beverage, but in general, if you have a caffeinated beverage of choice, you probably want to arrange to get some and bring it with you. There are beverages provided, but not necessarily when you'll need them or in sufficient quantity to ensure you'll get one.
I do find it odd that Brent recommends Denny's for late-night after-booze dining but lambasts the Moscone food as "awful". The food at Moscone West is far from stellar, but it's considerably better than the nearby Denny's. Then again, we all have different standards when we're sober then when we're three sheets to the wind and I've ended up there on more than one occasion myself, so...,
Personally, I never found the Moscone food to be that bad and lunchtime can be a great time for visiting the labs without having to give up a session.