If you want a nice cool marathon take Gore's advice and take public transportation to the start. Otherwise global warming will doom us to another hot marathon!
OK Seriously, I have driven from BWV to the start. To avoid trafic issues plan on leaving before 4 am. Otherwise you face a possiblity of long waits in traffic and a possibilty of watching the race through your windshield. Both times I have diven to the start I go by the bus stop and load my car. That way I feel less guilty about not riding the bus. Note that by driving from BWV to the start you take way one of the perks for staying at the resort and that is the ability to walk back home. One other note, last year the parking lot was screwed up post race taking over an hour to get out after I finished the full.