Shuttle Atlantis is scheduled to lift off on Dec. 6 at 4:31:44pm EST (exact second will be refined by launch day). This is the middle of an exactly ten minute long. Atlantis on mission STS-122 will deliver the long-awaited European Columbus science laboratory module to the international space station.
It is well worth it to go and see the shuttle launch, regardless of traffic or even if you can't get the absolute closest. There are just 13 shuttle launches left; everyone should get to see it once.
http://www.launchphotography.com/Shuttle_Launch_Viewing.html
This guide will give you a rundown on viewing the launch. Titusville is the closest offsite (free) location at 12 miles away.
The closest viewing is 6.5 to 7.5 miles from the NASA causeway but those tickets (tickets only since 9/11, unfortunately; it used to be free) are long sold out. However, tickets to view from the Visitors Complex at 7.4 miles from the pad are still available at
www.KennedySpaceCenter.com. The only asterisk is that the pad itself is not visible from the VC.
Please note: kennedyspacecenter.com is NOT a NASA website and the information on there is not always accurate or up to date.
The best website for launch dates from the Cape is:
http://www.spaceflightnow.com/tracking/
Good site to bookmark. They will also, starting early next week, begin to provide daily updates and a "mission status center" with play by play of the launch. It is a great place to check to see if the launch is ontime, the official weather forecast, etc.
From Titusville, at 12 miles, it is easily visible and you will hear it easily but do not go expecting a deafening roar. More appropriately, you should ask yourself "how many things can you hear from 12 miles away at all?" The shuttle's roar is clear from there. It shows just how powerful and amazing it is to send an 18-story building into space. (If you could get to the causeway, it is much much louder).
If the sound is more important than the setting, then the Visitors Complex may be better for you. It will be much louder there than Titusville. It also provides you with things to do during the day, though, yes, it will be crowded on launch day (like Disney ;-)
I hope you try! Good luck and feel free to ask any more questions.
Hope this helps everyone.