Hi Newfie Girl,
The two big Outlet malls are now both owned by Premium and are at opposite ends of I-Drive (the South one is actually on Vineland, but it's only a block off of I-Drive)
http://www.premiumoutlets.com/orlando/. The third option is Lake Buena Factory Stores, it is smaller than the Premiums and used to be lower-end (IMO) but has steadily improved its blend of merchants
http://www.lbvfs.com/.
The deals are similar at all three, so your best bet is to check the sites online and see what stores you want to go to. We usually stick to Premium on Vineland because it is close and has more shopping than you could do in a day. Deals are better at some stores than others.
From DTD, the Vineland location is by far the closest, and only about a 10 minute cab ride (longer during rush as the roads around 535 and I-4 get very congested). LBVFS is about 5 minutes further up 535. Not sure about taxi cost - we always have a car. If you want to go to the other Premium Outlet, grab the I-Ride Trolley
http://www.iridetrolley.com/ from the Vineland location for an easy trip. Fares are $1.25 cash or $4.00 for an all day pass. The trolley also stops at Festival Bay Mall if you want more conventional shopping.
Just remember that there is an overweight or excess baggage charge awaiting at the airport if you go too crazy. Can't tell you how many times we have been left furiously shuffling treasures between suitcases trying to keep everything within limits!!
Happy shopping!