You should be able to see the launch from any where on WDW property. Just face East about 15 - 20 seconds after launch and you will see it blasting towards space. For the best view, drive to Cocoa Beach ( 1 hour east). You would be 8 miles from the Launch site as opposed to 60 miles.
It is Amazing from the beach. The problem is, you never know if it is actually going to go off and then the traffic to get back to Orlando is a Nightmare taking up to 3 to 4 hours for a 1 hour drive.
If the launch goes off it is worth the traffic, if the launch is scrapped the drive home stinks.