Merlyn seems to make plenty of shows. I see him in Chicago each March, and last year caught him at both the NMRA convention and the O scale meet in Indy. Super nice guy, always friendly and helpful.
When you enter the hall for the March meet, the middle section is filled with tables running left to right. The tables on the ends of the hall run front to back. Merlyn is typically in the back half of the first row of front to back tables on the right, facing the middle section. I don't remember him having a sign. I just always look for the stacks of blue Atlas boxes. I hope that description makes sense.
Jim