I believe Mears Transportation also offers towncar service from the airport, and it may or may not include a grocery stop. Cab transportation on and around Disney property is pretty reasonable.
The Boardwalk grocery store is pretty decent in a pinch, though some items (particularly beer and wine) can be quite expensive with limited selection. Publix had a pretty good craft beer selection last time I checked.
Coming from Boston, I will say that the cabs in Orlando are quite nice and clean, and the drivers are usually very friendly. Any Disney hotel will call them for you, and they'll show up pretty quickly since they're all over property. Additionally, you can get cabs out of the theme parks at night (except for the Magic Kingdom, where you have to go to the Transportation and Ticket Center to get a cab rather than at the very front of the park).