It has been our experience that with the CP package deal and the priority seating for the show, we get in line about 30 to 45 minutes prior to the show. We have seen many times that the people in stand-by did not get to see the show. I would say that if you have your heart set on seeing it and don't want to pay for the dinner/priority seating, you should probably get in the stand-by line at least 1 hour prior to showtime. The stand-by line is (when facing the stage) the line to the right.
Good luck and it is so worth whatever you have to do to see it!
PS we are pretty frugal and we do the package every year. It gives us an excuse to have a great dinner with all the goodies and great seats for the CP.