I consider myself Agnostic, but who cares about titles. I was raised in the church, I still believe in intelligent design, but I do not believe in organized religion or any of man's interpretations of God or his word. Don't want to start a flame war, so that's as far as I'll go about me
That being said, I do agree with a few of the other posters in that I see "In God we Trust" as more of a historical statement than a generalization or a "rule". Being a strong believer in the separation of church and state, I would take issue if it were added to a newly constructed courthouse, or in this case, a government building. However, in this case, it's being engraved onto a visitor's center--so have at. "In God we Trust" is as historical to Washington DC as "Here you leave today and enter the world of yesterday, tomorrow and fantasy." is to Disneyland.