Personally, I always wanted a pass for the launch itself, but barring that, any place along the beach downrange would be good. The shuttles take off turning toward the south, so that means Satellite Beach, Indian Harbour Beach, Indialantic, and Melbourne Beach at the furthest - with the optimal balance of closeness (to see it as soon after launch as possible and see it somewhat large enough) and being downrange (to see it for a longer period of time) being Indian Harbour Beach.
Beyond Melbourne Beach, you'll still see the shuttle climbing, of course, but it'll be too small imho.
Keep in mind that this being the last shuttle launch it'll be utterly insane trying to find a place to view the shuttle. Adaptability, flexibility, and good humor will be essential.