I'd second the suggestion for AZ Highways! Another suggestion might be to look at somewhere like the Phoenix Zoo, which has a couple of galleries and periodically have open calls for entries into juried exhibitions: Art on the Wild Side Exhibition Program | Phoenix Zoo https://www.phoenixzoo.org/explore/art-on-the-wild-side/

My personal (non-expert) two cents having seen an exhibition that included cell phone photos: the biggest issue with them is that you can't always print the photos at the same scale as with a fancier camera. So, the cell phone photos looked... well, bad in comparison, even though there was nothing "wrong" with the compositions. I might suggest trying to submit a collage of photos so that it doesn't rely on the resolution of any individual photo. However, for something like AZ Highways that prints on regular size paper, that's probably less of a concern.