RenegadeMonk, one point I'd suggest is to travel with your relatives in a group. As your relatives are more familiar with the local scene, they would know where you can go, and places not to go.
That way, if you do get in a bad situation, you won't be by yourself. You're less likely to get lost as well.
I've been to the Philippines on and off for the last twenty years or so, usually in and around metro Manila. Although a friend of mine did describe a hairy story once, I personally have no horror stories to speak of.
I'm not saying that bad things don't happen, or have never happened there. I just don't think it's any more common than you might expect anywhere else in an urban setting in the U.S.
Personally, I'd avoid carrying a knife with me to the PI. It's just way to easy to buy one once you get there, there's no need to deal with any hassle bringing it with you on the plane. Once you get ready to leave at the end of the trip, you can just give it away, or ditch it.