To somewhat fix this, edit /etc/gtk/gtkrc.utf-8 and change the fontset definition.
style "default-text-better" {
fontset = "-bitstream-charter-medium-r-normal-*-*-100-*-*-p-*-iso8859-1,\
--bitstream-charter-medium-r-normal-*-*-100-*-*-p-*-iso8859-1"
}
class "GtkWidget" style "default-text-better"
This will fix the menus, at least.