Are you staying at one of the Disney Hotels? If so, the free Disney transportation is quite convenient. In fact, if you are staying at the Beach Club, the Yacht Club, the Swan, the Dophin, the Boardwalk Inn or the Boardwalk Villas, you can either WALK to EPCOT or take a boat. The other on-site Disney hotels all have either bus service or monorail service to the the park. IMHO, Disney transportation is much more convenient than driving a car.
EPCOT is one big place. If you do drive, you will leave your car in a large parking lot and then hop on a tram that takes you to the gate. Once inside the park, you walk everywhere. Wear good shoes!
If you are staying off site, your best option is to use the main EPCOT parking lot. The EPCOT Hotels discourage the general public from using their lots (so that their guests have a place to park). Many of them will turn the general public away or offer them a three hour parking pass to those who just want to eat or shop in the Hotel.
Hope this wasn't too much info - your question made me think that you might be a first time visitor. Enjoy the trip!