Depends on what you mean by 'work' mate. Diving in the philippines is great - but keep in mind that a local DM can be gotten pretty cheap (in the range of about $10 / day). You need to justify why it is worth having you for more money -
Better knowledge of the area - doubtful.
Better Skills - you are going to be a rookie, a lot of the DMs i see are in their 30s, even 40s..
Availability - these guys are willing to work damn hard for that $
Being 'Western' - Might be a pull for the owner / owners but unless you have language or other specific skills that draw in customers, you are just a needless expense to them. Also, need to think about the legality of your working status in the country (you realize you aren't supposed to work as a tourist right?)
I'm not trying to be down on your dream, just want you to be aware of reality. The diving industry sells the DM course and onto Instructor to you based on the 'exotic locations and opportunities that abound'. The shops are likely to hook you into their course with the same idea - but are there real jobs tied to the dream? I'm not entirely sure but when i look at most of the (foreign owned) dive operations around the philippines i see a foreign owner(s) and a majority or total team of local DMs. I've also seen a lot of people buy their way into a dive shop partnership to live the dream.
You know the old adage right:
How do you make a million dollars in the dive industry? Start with 2 million
If you are really wanting to get hired then when you are searching for shops to do your course with make sure you find foreign DMs / instructors working there. If you do, make sure to take them out for a beer or 2 and get the real scoop on the potential for jobs before you plunk down any money.
Good luck - you are going to need it and a lot of hard work!