Is it better to exchange money at the airport, or locally (in town)?

Never do it at the airport. Even if you have to, exchange at least $100 there and do the rest in the city.

The best way is to send money to a Philippine bank account of someone you trust, with no fees. Then withdraw it once you're in the Philippines, and order cash from Chase Bank. They charge a very small fee.

The bank rate is good and safer than money changers. It doesn't make sense to save a few centavos looking for a better rate when you think about the time you waste.

Just withdraw from an ATM. That's probably the best exchange.

The small "black market" money changer stands are better… but they're usually pretty picky. They want big bills (over $20), and the bills have to be crisp and flawless.