Well, we just came back from our Anawangin trip and I could definitely say there were no jellyfish there. However some other notes:
1. During Holy Week, daming people. But our tour guide told us on usual days, crowds are thinner.
2. Anawangin is good but not for babies/toddlers. Why? You'll just add to the garbage problems there by bringing disposable diapers.
3. Bring a bottle of shampoo and not the ones packed in sachets. This is because you'll more likely to bring back home that bottle of shampoo. There were lots of empty shampoo sachets scattered all around.
Just to note, I would highly recommend our tour operator, pinoycaravan.com. They will make your stay there pleasurable as they will take care of all the things that you need; transportation from Manila to Anawangin and back (includes van and boat fares); tents; food (lunch, dinner, and for the next day, breakfast, lunch), drinks (with ice!), bonfire at night where you could toast marshmallows and hotdogs that they will provide. Also included; alcohol! Emperador Light!

The package also includes a hiking trip around Anawangin and boat rides to the nearby Capones Island. Well worth it and their service is great.