Cantabaco is mentioned in the 8a crag data base. One possibility is of course to check the Tick List and write some messages to the guys who have recorded ascents there.
I got a message from a climber in the philippines, so I'm posting it here if anybody else is interested =) hello Magnus The best place
to go both climbing and diving will be in Cebu. and its easier to fly
there too. the crag is only an hour away from the city. i can hook you
up with some local climbers there to go with you as of now we dont have a
guide book, we have lots of 5.11 - 513d routes. As for the diving you can check these places: Malapascua, Moalboal, and Pescador island.
Climbing in Phillipines