I grew up in the PI, and let me just quote this:
Other than that, I would NEVER want to road bike in the Philippines (especially Manila) without a group of people and a sag car blocking the traffic behind me.
Listen to him.
There has been a sharp rise in the number of motorcycle owners too in the past 10 years. The Cyclist's place on the roads of Metro Manila has gotten smaller in the past decade. Just to be on the safe side go find a place on the countryside (tons of great places recommended here).
Else, it's playing Russian roulette with anyone from a motorcycle to a bus. A game which you wouldn't want to play if you want to live longer.