Facebook may have started out as a social network for college students, but, by now, nearly everyone with an internet connection is using it. The minimum age requirement is 13, and there is reason to believe it is being used by all other age groups.
Facebook doesn’t publicly release data on their most popular age group, but a survey by Pew showed that social networking is most popular with the 18-29 age group . Its popularity decreases with age. It is least popular with those 65 and older.
I can assure you that, no matter what age group you’re targeting, there will be more than enough of those users on Facebook.