Alright, not going to lie: taking a child under the age of two to a full-on movie in a for-real movie theater is some serious business.
All the blog posts I've read on the topic say to wait until 2 1/2 or 3 at the earliest...but you know what? I think provided you follow some basic Laws Of Common Sense And Respect For Your Fellow MovieGoer (below) this is a to-each-his-own situation, and a) we really love going to the movies, and it's a special thing for our family, and b) our son actually seems to have an unusually high attention span for anything involving motor vehicles (he can happily sit through the entirety of Cars when we watch it...over and over and over...at home).
So despite the fact that yeah, he's a little young...to the movies we go.