Since WDW is such a huge place, you might want to check the driving directions from Sanford (SFB) to your resort's address. We're flying into Sanford next month and the yahoo map said the trip to POR would be about 44 minutes.
I also wanted to suggest renting a car for the whole time. If you're accustomed to getting a town car service, you might find that the cost to have a car available 24/7 is not much more that the town car plus tip.