I think it depends some on your location, cathy. I love "Hold On" and I can get away with doing it here in South Dakota. But when I attend auditions in bigger areas, I have been told to stay away from it, and most songs from this show.
But as far as TGIMTB goes, you're a young girl aren't you Gav? From my experience casting directors would rather you sing something age appropriate even if it is a little over done. There aren't many solos for children/young teens out there, so of course when they are auditioning young people they are going to hear the same songs over and over.
(-this is coming from the girl, who at the age of five, practiced singing Be Kind to Your Parents for an A Christmas Carol audition, but two seconds after entering the audition room, decided that an acapella rendition of You've Gotta Have A Gimmick was a much better choice.)
"A wonky eye, you've got my friend."