Hi Becky - Thanks for sharing.
Great start and a unique subject matter for sure
I would make the poster so that the most pertinent info jumps out at the reader - as is easily and quickly grasped.
With that said, I would remove the blue focus, and emphasize the sites, and the Suitable sites.
Legend - go for a standard legend, maybe vertical group of colored boxes with the most common types at the top (yellow and purple)
Suitable Sites - instead of pushpins, use callouts with leader lines and big labels since you are communicating you have found a handful of sites.
Map - Label Major Highways, rivers, and major towns/cities. If there are urban areas, and you have urban layers, maybe show this.
Pie size - instead of the gradient, show the average sizes, maybe there are 5 or 7 of these, and indicate their value. This way ppl can be sure they know the value of a given pie.
(imho, I would lose the 3D pie and go with a 2D pie). Cleaner I think.
Bump up the text blocks - nice and clear.
Looking forward to your revision! -Chris