Hello, have not stayed at Mango Key but drive by very often during the winter. MKey is an older Condo community located very convenient to Disney off of Lindfields Blvd.
If you Google Map "mango key kissimmee" it will take you right to it on map or satelitte. Notice you are just south of Hwy 192 which is the main highway east-west past Disney World.
Disney is 7 miles long so there a several ways off 192 to get into Disney.
For you, absolute easiest and quickest is to hop on Toll 429 just east on 192 for about 75 cents each way and go a mile north and into Disney.
To save the toll go about a mile farther east and turn on Black Lake road. Take BL road a couple of miles till it ends and take kind of a tricky left turn onto Sherberth Road...follow Sherberth about a mile, make a couple of turns and you come to stop light inside of Disney. Turn RIGHT (Osceola Parkway) and follow the signs to all the parks. Animal Kingdom will come up quickly, so be ready. Turning left will get you to Animal Kingdom LODGE which is great. Boma's famous buffet is there and make sure to wander outside and see the lodge and the animals.
To exit the Parks, follow the sign from parking lots to ANIMAL KINGDOM. Be ready for a couple of quick right turns. As you approach Animal Kingdom stay in LEFT lane to ANIMAL KINGDOM LODGE.
You will be back at the stop light...turn left on Sherberth and this time stay all the way to 192 and turn right to get back to Lindfield's Blvd. It is hard to see the Lindfield's turn at night as the brick sign is pretty dark so watch closely for the left turn lane.
Mango Key always looked very nice, clean and based on the economy you should be able to get a 2-3 bedroom condo for less than $90/night easy if not less, If they want more, there are better deals around.
Enjoy..Ted