I know nothing about taxis in the WDW area.
Do you know that you can get a grocery delivery? The service fee will be cheaper than a taxi, and you won't need to waste your vacation time getting to and from a strange supermarket to search through and stand in line in.
www.Goodings.com -- Gooding's is a local supermarket that delivers for a $20 fee. They deliver directly to Bell Services (you'll never see the Gooding's delivery person), and then Bell Services delivers to you. As a result, you don't need to schedule your delivery and thus you don't need to tie yourself down to your room and wait for a delivery that may or may not arrive on-time. If you're not in, Bell Services stores the stuff for you, and even keeps the cold stuff cold. Gooding's will NOT deliver alcohol.
www.WeGoShop.com -- a stand-alone delivery service. They shop where you want them to. You must schedule the delivery, as they must deliver directly to you.
www.GardenGrocer.com -- another stand-alone delivery service. Their methods are a hybrid of the above two. Their usual way is to schedule a delivery directly to you, but upon request they are happy to plan to deliver to Bell Services so that you don't need to sit around and wait for them.
I don't recall ever reading a substantial complaint about any of the above places from a dissatisfied customer.