Greetings David,
Beautiful pictures of the Juglans guatemalensis. Unfortunately, I'm not an expert in international forestry or direct import marketing of international wood.
However, the United States Department of Agriculture has a state by state directory of extension forestry experts http://www.csrees.usda.gov/nea/nre/pdfs/forest_directory.pdf
This list can provide you with direct contacts to coastal states that may dabble in exotic wood imports. You should also check with the Guatemalan government to see if they have a natural resource agency (forestry) that may be able to assist you in identifying local markets or log export companies.
Sorry I couldn't be of more assistance.