Odyssey mate, come on up we shouldn't be too hard to find. From the "real" trailhead (ie at the top after you get off the Buddha bus/ taxi/walk up) just follow the crowds up the only trail there is. You will need to pay an enterance fee right here too. It's a good walk, about 30 mins I think (been a while so maybe wrong). This will bring you to the unmistakeable Insubong camp grounds (permitted clubs only not public) and rangers hut. The climbing starts up the back from here, and can be a bit tricky to findif you are alone/ 1st timer, but any climber will point you the way (up and leftwards on small trail)...it's only a few minutes further (but not on the main hiking trail which goes straight down the valley past some porta-loos). I don't know where the boulderers will be exactly, but I'm guessing right inthis area near the campground (right??) so jot down a few folks cell numbers and call in when you arrive.
quem deus perdere vult, primus dementat