There is something that I've wanted to know for a while now. So Valeris won't tell the names of her co-conspirators, so Spock uses a forcible mind-meld on her to get the names. Then Kirk asks for the location of the conference, so Spock digs deeper (which causes great distresses for them both). She doesn't know, so Kirk contacts Sulu, and he knows. Why didn't Captain Kirk or Spock just get in contact with Captain Sulu for those details?
Sulu wouldn't have any idea about who the conspirators were.
Right. The mind meld was used initially to find out who the conspirators are. It was only after
they learnt that Valeris didn't know the location that they called Sulu. There'd have been no point asking him about the conspirators as, unless he was part of the conspiracy himself, he wouldn't know anything about it.