When we took the SEGWAY tour in May, we too were told to meet at Guest Relations at the front of the park (by the CM at the Beach Club desk). THAT'S WRONG! It's the Guest Relations right near Spaceship Earth.
We always enter through the International Gateway. In May they didn't have a list for the SEGWAY tour but they let us in without a problem.
In October, they did not have our name on a list either, and again just let us through.
However, in October we had the early tour and got there a little before 8:00. Security was there, but no cast member to let us in. A cast member got there just about 8:00, so don't bother to get there too early before 8:00.
Liked the tour the second time just as much as the first.