kdm:
There are lots of transportation options other than a cab. I don't really have an idea how much a cab would be, but it's a 50 minute to an hour drive, so it would be LOTS!
Dave_from_Marietta has lots of rental car options on his site. I'm a brick when it comes to the link things, so just look for one of this posts on here, and it's got his page in his signature (Thanks Dave for doing this)!
ALso, Disney does bus transfers. For our family of 4, it was cheapest to rent a car one way.
Good luck!