The Lynx Bus 111 used to go from Disney World to Florida Mall. That was discontinued about three weeks ago, which is bad in a number of ways since new cast members were also using that bus to get to Disney University for orientation classes. If you want to take the long way around, you can catch Link 50 from Magic Kingdom to Lynx Central Station and then catch Link 4 or Link 7 to Florida Mall. While Orlando wants to be seen as a world class city, we have a public transportation system that is an embarassment. Tourists from Third World countries are shocked at how badly it is run. This is a problem for local businesses too because so many of our fast food places need workers around the clock as well as the theme parks and hotels.
I have seen tour groups at Florida Mall, though they are mostly teenage Brazillian girls so I am not sure if just anybody can go on the bus with them. Except for those staying at the Florida Hotel at the mall, they are almost all Disney hotel guests so maybe you could check with the concierge at Disney resorts and see if the concierge could get you added as a temporary member of one of the Brazillian tour guides' groups.