Let me see if I can add something. With the 500, planning is everything, the 2005 race will be our 14th. So try this:
#1 - I would get of the ship as soon as they start disembarkment
#2 - Make sure you have a map, like Dave said you can bail from I95 to US1 if necessary.
#3 - If planning to go to Orlando on the way back, you will want to park on the west side of the track. They turn alot of the roads to one way after the race. DIS will send the traffice plans with your tickets, and are probably on line as well. If you are not in a hurry, then if may not matter, you can hit the trailers. Remember traffic in front of the speedway will not move for at least 30 minutes after the race.
#4 - Get there early, we stay beachside and leave our condo @ 5:30 am. We leave for home after the race and drive home, so parking location is very important to us.
#5 - If there is a special guest again next year, it will take a little longer to get into the track, wasn't too bad this year. The Air Force One fly over was the highlight of the race for me.
#6 - I am guessing the earliest you maybe able to get there is about 10:30 (and that is being generous), if you chose to pay to park, expect at the least $30 and can be up to $50. The cheaper lots go early.
Let me know if you have anymore questions. Personnal I would prefer a 7 day
DCL cruise

. Oh that reminds me, better get the 500 renewel in.