I think you're confusing the Pacific Pinball Expo with Pin a Go Go.
The Pacific Pinball Expo was held in October this year and will be on Friday September 23rd through Sunday September 25th, 2011. http://www.pacificpinball.org/exposition
Pin a Go Go is usually held the second week in May. The new date for 2011 has not been posted on their site. http://www.pinagogo.com/