Hi!
I don't have any personal experiences with taking a taxi from WDW to SW. Cab fare from the airport to WDW is in the $40-$50 range one way, just to give you a point of reference. I'm pretty sure you can take a Lynx bus from WDW to I-drive and then grab a trolley, but I can only imagine how long that would take... yikes! (But the trolley does stop at SW once you get to I-drive.)
There are Mears shuttles that can take you back & forth to SW & DC. According to their pricing sheet, it would cost you $16 r/t per person from WDW to SW or DC. So $16 x 3 = $48 per day.
http://www.mearstransportation.com/pdf/Rates2007.pdf
If you opt to take the shuttle, either contact Mears directly to reserve, or ask the concierge staff at CBR to make the reservations for you.
I'm reasonably certain you could rent a car for the same the money or less, and it would give you the freedom to come & go as you please. I know there are rental car locations in the WDW resort, so you could easily just rent a car for those two days. I just priced out an economy car through Alamo to be picked up and dropped off at the WDW Dolphin hotel the week of Sep 20. The two day rental with taxes and fees came to $73 without any coupons or rate codes. $96 for shuttles vrs $73 plus gas and parking at SW. So you could save a few bucks by renting - not enough to consider it significant however. (To get to the Dolphin, just take the bus from your resort to the MGM, then hop a boat or walk to the Dolphin.
Consider this: if you get done at SW or DC early and want to shop the outlets or to have dinner offsite would be so easy with a rental. Or you could just do a grocery stop on the way back to CBR, and buy water, juice. snacks etc for a lot less than at the resort store.
Good luck!
Lisa
