How do I find out who is also contributing to OSM and communicate with them?

If you have an account on openstreetmap.org and go to http://www.openstreetmap.org/user/<your_username_> , you will see mappers located near you in the map view on the right. For this to work you would have to set a location in your account preferences.

Another good way would be to have a look at "Who did it?" on http://zverik.osm.rambler.ru/whodidit/?zoom=11&lat=14.63741&lon=121.05136&layers=BTT for your area of interest and look who has edited there in the past, and then contact them through OSM.

If you want to search by activity centre, then Pascal Neis has an excellent map that should be useful.

Another way is to introduce yourself at the Openstreetmap Philipines mailing-list and see who replies.

Welcome!

Finding other people mapping in your area: Best look at the two tools listed in the bottom section of the wiki page Nearby users.

Communicating: When you are on someone's user page (example: my OSM.org user page), then you can use the link "send message" to send a message to this user who can respond then. You can have a look in the user's recent edits there to see if he is really active currently.

Adding a "note" in an area can help connect you to another local mapper. Reviewing nearby "notes" can help you find other people who are active in your area.