Just so you know - you WILL get lost, at least once. You WILL make a wrong turn. I make wrong turns sometimes even at home!
The roads on Disney property are well marked with big signs.
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To get to ASMO from the airport:
Getting from the airport to Disney is pretty easy. There are two major roads that you can take:
1) The north airport exit will take you to State Road 528, the Bee Line Expressway. Take this West to I-4, take I-4 West, and get off at Osceola Parkway West. Exit onto W. Buena Vista Drive, heading West; W. Buena Vista Drive. dead-ends at the All-Star resorts (all 3 All-Stars have one guard shack/security gate). There will be signs directing you to the All-Star resorts.
2) The south airport exit will take you to State Road 417, the Central Florida Greenway. Take the Greenway West until you get to Osceola Parkway. Exit onto W. Buena Vista Drive, heading West; W. Buena Vista Drive. dead-ends at the All-Star resorts (all 3 All-Stars have one guard shack/security gate). There will be signs directing you to the All-Star resorts.
Both the Bee Line and the Greenway are toll roads; you will need about $3, preferably in quarters, for either of them.
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To get to SeaWorld and Discovery Cove from ASMO:
Take the exit road from the All-Star resorts out to Osceola Parkway (pass the guard gate, the entrance ramp is on the left just before McDonalds). Take Osceola Parkway East to I-4. Take I-4 East for 6 miles to exit 71, the Central Florida Parkway, East. SeaWorld's entrance will be on the left, about 3/4 of a mile.
The entrance to Discovery Cove is just past SeaWorld, but on the right side of the Central Florida Parkway.
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To get to Downtown Disney from ASMO:
Take the exit road from the All-Star resorts. Do not turn onto Osceola Parkway, keep going straight; W. Buena Vista Drive takes you all the way to Downtown Disney with no turns. It's about 3 miles, and Downtown Disney will be on the left.
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General hints:
Make a snack stop on the way from MCO to ASMO. Pick up whatever snacks you will want to keep in your room, and also pick up a cheap folding cardboard sunshade for the car's windshield - and USE IT! The Florida sun in August will turn your car into an oven, and the sun shade will help. You can also leave the windows open by 1/2" or so to let the heat vent a little; this can let rain get into the car, so don't leave them open very far.
When you first get into a hot car, roll all the windows down for about 5 minutes while the A/C gets cool; this allows the hot air inside the car to escape so that the cool air from the A/C will be able to take its place.
Take a streamer of some kind with you, and tie it to your car's radio antenna. This will mark your car and make it easier to find in those huge WDW lots. Also take a notebook and a pencil, and write down where you park every morning so you'll know which parking lot tram stop to get off at!
When checking in at ASMO, ask for a room near the parking lot. It doesn't matter if it's far away from Cinema Hall, because you can drive around to Cinema Hall in the mornings, park in the Check-In lot while you have breakfast, then drive to the parks.
Resort hint: The Love Bug and Mighty Ducks sections of ASMU are actually closer to All-Star Music's Melody Hall; you can walk or drive there for breakfast or to fill your mugs if you like. When staying at an All-Star resort, you are free to go into any of the three main Halls (you're also allowed to swim in any of the All-Star pools).
Google Maps has the best coverage of the area, as well as aerial maps. Use them to get familiar with road names and decide routes. You can also use Local Live to get a better idea of what specific places look like. Click the link in my signature to go to my Maps page, which has maps of all the WDW resorts and parks, and links to both Google Maps and Local Live maps of each place as well.