As it happened, I switched to N scale in about June 1990, when my new house had a loft of about 12 x 17 and I happened to notice an unfinished N scale layout of that exact size in the Sunday Classifieds (how old does THAT sound?). Having an HO shelf layout in my old house garage, I bought it and spent several years fixing it up, and even enlarging it after one move (unfortunately, back to a garage, which worked until one of those DFW summers where constant 100 degree heat buckled up some of the track).
So, I think I bought one of the first few issues, perhaps backdating to the very first one after I discovered it at my LHS. I recall an article on N Scale of Nevada frames, for one, if that helps date my first copy.
So, we sort of grew up....or is that smaller?....together. I have enjoyed it ever since 1990.