(I have no idea who Lynn Collins is, so no thoughts on her as Dejah Thoris.)
Utah's an interesting and, I think, right choice. I remember years ago when Harry Knowles was in some way involved in the attempts to finally film this novel; when he went with the Alamo Drafthouse's Touring Road Show to show a movie on a portable movie screen in Utah's Monument Valley, he said there were all sorts of corners of that park that could be fantasy-Martian landscapes. Now we're closer to seeing those fantasy-Martian landscapes on the big screen. Cool.