Well, not many people have actually BEEN to the island. They could easily be considered experts at it by now, even if in reality they're not.
Though to be honest, everything goes to shit at Jurassic Park. This is pretty much common knowledge. I don't think a single one of the original cast members would even risk stepping one foot on that cursed island.
..Honestly, I don't see why anyone would. It's not like dinosaurs are constructing a crude suspension bridge to the mainland or anything.