I've watched a lauch from the NASA causeway and it was amazing! A real pain to finally get in place, but well worth it.
The rough price is in my sig but that was a year ago and it did include breakfast with an astonaught.
You can get tickets that allow you to watch from KSC without going to the causeway that are cheaper but I personally wouldn't pay for those.
If you go to the causeway it is the closest view you'll be able to get of the launch, but it's very rustic so bring your own foldable chair and remember sunscreen (i got burnt, not much fun).
Everyone is right BTW there is an even chance that the launch will be postponed, so you may not get to see it at all (our launch was postponed from December until feb! But luckily I has some cash squirrelled away and I did a lightning trip over to see it).
If you want any details, just ask!

(oh, and watch the youtube video

)