Got the info from the link posted above by Evocus:
http://insideevs.com/monthly-plug-in-sales-scorecard/
Unfortunately it's not broken out geographically from this source.
I tried looking for more info on the Ford media site, no luck. All I could find there are total Focus numbers in the U.S. - 24,929 for March, so FFEs made up for less than 1% of Focus sales.
http://media.ford.com/images/10031/March13sales.pdf