I went to SONG (joya II) last night and because there were a couple of us who were vegetarians (one Buddhist, one allergic to fish), we wanted to know about the fish-sauce-less options. Our waitress said that many things could be made without the fish-sauce (but sadly the curries could not).
However, when I went up to double check with the host about this, he said that most everything would still have a little fish sauce because of the pre-mixed bottles of sauce that they use. They would be happy not to add any additional fish-sauce, but there would still be some in it.
This was disappointing to hear, but good to finally get the truth. Many people are allergic and the philosophy of "just a little" means "none" could be law-suit worthy.