If you are heading anywhere in Florida you might consider timing your trip to coincide with a shuttle launch.

You can pay to watch from inside Cape Canaveral but unless you can get tickets to watch from the causeway (which sell out very quickly) you will be watching from the visitors centre and won't actually see anything of the shuttle until it has risen above the trees that block your view of the launch pad.

The alternative is travel to Titusville which is across the river from the launch pads. You will be further away and you can't really make out the shuttle very well before take off, but as you can see from the picture (taken with a zoom lens) the view isn't too bad.

The two big advantages are that it is free to watch from Titusville and there are no restrictions on when you arrive and leave, however you do want to arrive in time to get a good viewing point and the traffic is quite bad after the launch.