Head toward Cocoa Beach just south of the Cape. There are areas all along the causeway. I keep going if I'm early 1 to 2 hours, and drive to the area where the cruise ships docks. The north area. I never had to walk too far, but the earlier the better. Pack a cooler, it's kind of carnival type setting waiting for the launch. The dock area launch sound delay is about 50 seconds. So it's close to 10 miles fron the actual launch pad, across mostly water. People all over will have the countdown on their radio, but it wouldn't hurt to carry a portable radio.
The other poster is right, don't bet any money on the launch date. I was over to see the "Deep impact" launch. ( the one that just hit the comet July 4th) Deep impacts liftoff was right one time, but much smaller that the 3 shuttle launches I've seen.