I suppose we ordered at around 2 weeks away from our trip. The only risk in waiting is that your preferred delivery time might be booked and you'd have to be flexible about it.
Just go to vons.com and click on "Grocery Delivery." You will have to create an account. The only tricky part is ensuring that you put the right address info in for your DL hotel for delivery ... it seems like when I did it, it wanted to default to my home address. Be sure you don't order any alcohol if you won't be there to sign for it, or your whole delivery will be sent back. We did this -- were told by the front desk that they would sign for it on our behalf even though it contained alcohol, but the bell desk ended up getting the delivery and refused it.
Amazon is a great option as well as long as it's all non-perishable.