Vons delivers. We had them deliver to GCH last year--water, juice, milk, fruit, cereal, cheese, crackers, etc. plus paper towels and plastic spoons. We asked for delivery within the hour and a half just before we expected to arrive. The bell desk held the order for us-- it was tightly packed in a cardboard box, so the refrigerated items stayed cold. It worked well. You order online with a credit card, using the hotel's address as the delivery address. Call the hotel's guest services a few days before, and let them know you are expecting groceries.
There are also some items for sale in Whitewater snacks and in the gift shop in the lobby-- milk, juice, pastries, etc. Of course, they're priced a bit higher, like a convenience store. We especially liked Whitewater snacks for fresh, cut-up fruit and veggies-- it is a great little cafeteria.