I've yet to do Sunken Temple of Quarn.
I've had no problems with the people I've ran into when I've been new to an instance.
This morning I just finished Cape Westwind with a group of 8 players who were all new to the instance (granted this was far easier then Garuda) and even though we died twice in the attempt no one complained and everyone offered up good suggestions on what to change up in our next attempt.

If someone wants to bitch and moan about a person being new to an instance and not help them learn then they're always free to leave to sit in a queue for another group.