According to some spoiler information, the racers head to the Pit Stop from the province of Laguna. It's around an hour or so, maybe more, from Manila. It's possible that the other Roadblock task is there as well, but if it's not there that's an awful long way to send the racers out. My guess is that the carabao plowing is the last task they have to complete in the Philippines. Roadblock could well be the balut eating; it fits with the other food challenges so far. Detour could involve the peso-collecting task mentioned in the final 3 spoiler thread.