http://en.wikipedia.org/wiki/You#Informal_plural_forms
Informal plural forms
Despite you being both singular and plural, some dialects
retain the distinction between a singular and plural you
with different words. Examples of such pronouns sometimes
seen and heard are:
...
you guys – U.S.,[2] particularly in the Midwest,
Northeast, South Florida and West Coast;
Canada, Australia. Used regardless of the
genders of those referred to
...
(I live, work, and went to school in Northeastern U.S.)