When we come in on I75 we get onto the Ronald Reagan Turnpike (Hwy 91) at Wildwood. We go down to Hwy 429 and go south. We get off and come into Disney on the Western Way. This brings you into Disney at Coronado Springs. Take a left on West Buena Vista Drive and then left onto World Drive. You want to be in the 2nd lane from the right when you pass through the entryway at Magic Kingdom. As soon as you go through the entryway, immediately move over to the right lane (the bus lane) and your turn to the right onto Vista Blvd. The Fort is just a little way down on your left. This way is toll roads but worth it to avoid the heavier traffic pulling a camper.
Hope this helps.