Lotta people here on the boards suggest ordering your groceries online from Vons or Albertsons. We did it when we stayed at GCH, it worked out great. We ordered a rack of water, plus milk, juice, yogurt, fruit, cereal cups-to-go, and snacky things (plus paper towels, and plastic spoons for the cereal and yogurt). You can have them deliver to the hotel, within a 1-1/2 hour window, and the bell desk will hold it for you if you're not there yet. It's a great money-saver, especially for the water, which is like $3.00 a bottle in the parks and hotels!
Somebody said they even googled a discount code to get free delivery. I think it's 9.95 usually, or free for over $50.