There are rental car companies on site at MCO.
National and
Alamo have cars right at the airport so its easy to get to.
Alamo is the current "Official" rental car company of Walt Disney World. Which means they have a longer line then National.
I think Dollar may also be onsite, but I am not sure.
As far as driving from the Airport to the Resorts. Its not that bad. The person at the rental car company will tell you how to get out of the airport on to the highway, and then you just stay on the highway until you get to the Disney World Exits.
The thing to remember about driving around Disney World is that Disney has a funny sign system. Disney groups all the hotels by what park they are closest too.
So Animal Kingdom Lodge, All Stars Sports, Music and Movies, and probably Pop Century are all Animal Kindom Resorts.
Swan/Dolphin, Boardwalk, Beach & Yacht Club are all Epcot resorts.
and so forth... if you know which park (including Downtown Disney) your resort is nearest too, you will get signs with details which way to go as you get closer to the park, otherwise they will just say EPCOT etc.
I hope that wasn't too confusing.
Cindy in NY