A small update on Cheung Chau:
I had my doubts about Cheung Po Tsai Cave in the beginning; it's a pretty long run with a backpack from the ferry terminal (2km, with a stretch over steep inclines), and cameras couldn't possibly fit into the crevices to get into the hole. But I managed to talk to some eyewitnesses today, and yes, it is possible to confirm Cheung Po Tsai Cave as one of our Cheung Chau destinations!
The eyewitness accounts are similar to those from Thailand and China from the past few seasons. Huge crowd of production with about 20 people; they bought three or four boxes of drinks from local grocery stores. It was a pretty big crowd and it was a Saturday in the start of the school holidays (when throngs of visitors descend upon Cheung Chau), so it was difficult to discern between individual teams.
One interesting thing of note: while running to Cheung Po Tsai Cave, a man twisted his ankle and had serious problems; an ambulance was called and there was a bit of a delay. It's unclear whether this was a member of the crew or a racer. I checked out the hospital on the island but didn't come up with anything.
The photos of the teams were taken on the praya outside Wai Yan Memorial College, with teams running west towards the cave. From what I've heard teams didn't actually enter the cave. Didn't find anything suggesting they went anywhere else on the island, although it would be pretty lame to just go to Cheung Chau for a clue box outside the cave.