Hi Jennifer,
It is very possible to have the adoption completed by the end of the year but expect the unexpected. A lot depends on how fast you can get an approved I600, FBI Clearance, finish your homestudy, how speedy your Guatemala attorney is and how experienced your agency is with Guatemala adoptions. I wish you the best of luck!!!
Have you heard of the "BIG LIST"? It's a list of over 2000+ people who have or are going through a Guatemala adoption. It's different from most boards and is full of great information.
http://maelstrom.stjohns.edu/archives/guatemala-adopt.html
Michelle