My question is: could I install the AC on the lead of the attic access,
with the face down. In that way the ~exterior~ would be the attic and the
AC would push down the cold flow air. The lead for access to the attic is
on the wardrobe, which is next to my bedroom where I need the AC.

Sure can. Let me know when you do and I'll get a six-pack and we can drink
and watch the redneck entertainment when you turn it on.