While supposedly camping in Bunol is not allowed for the La Tomatina festival, five of us spent 2 nights camping for the 2010 festival yesterday. We slept in two different spots. The first night we slept down a driveway in a field (take a left at the roundabout at the bottom of the hill and walk about 20 meters). The 2nd night we walked halfway up the main hill toward the train station and set up our tents in the park to the left (if walking up) of the main road. The ground there was extremely hard, but the place was lit and fairly secluded. Whereas the first night, we spent all night listening to raging techno music from a nearby club — the 2nd night was actually quite peaceful with a water fall right next to our camping spot in the park.
So it is possible to stay in Bunol for La Tomatina — you just have to be resourceful and willing to tough it out in the wild. If we had to do it all over again, we would have slept in the park both nights of course, and would have brought more padding to sleep on top of so our backs didn’t ache so bad in the morning. Oh well; live and learn.