Yup... get a prepaid SIM card first (it's dirt cheap - haha) to evaluate if you have a good coverage at home or in your office.

In Ortigas, there are rare times when the network was very congested... maybe once every two months? Most of the time it is manageable...

In Bulacan, this is more frequent (since where I live is has one of the highest call rates in the country)... but I can still manage to place a call. If there's an emergency, I just use my wife's Globe line (well - there are time now too that Globe is congested).