You can use any agency you want to. My friends are using new hope in seattle for international. We are doing domestic, so I don't have any other international agency experience.
We used a wonderful SW, his name is Brian:
http://www.ahomestudy.com/contents.html
He is down near Tacoma, but will drive anywhere (we are up in Whatcom County). He is wonderful and has adopted 2 girls from China!
Good luck to you!