I totally forgot about the NMAT part of your question. About the thing you found on the internet about the nmat being held in march of this year. If I were you, I'd call the Philippine Consulate General in New York City (212-764-1330) and tell them that you are interested in taking the NMAT. They probably refer you to Mr. Jose Ramos (if not, ask for him/his number). He's the guy who's responsible for administering the NMAT in the East Coast of the US. And again, if I were you, I'd call ASAP, because you need to register and get all the paperwork done before they'll let you take the test.
As for how it compares to the MCAT, I found the NMAT somewhat easier. Whereas the MCAT tests you on concepts and application. The NMAT is more on concepts. It's composed of Math, Physics, Bio, Verbal, Social Sciences, Visual Acuity, Observation, and other things. It felt more like a combination of the MCAT and portions of those basic skills exams from High School that I took.
But I also found the NMAT much more physically exhausting than the MCAT. Where you have 15 minute breaks in between sections on the MCAT, with the NMAT, you show up at 8am, go thru the 1st part of the test (200?s) in 3.5 hours straight, 1hr break for lunch, then another 3hrs (~175?s).
I took the MCAT in August of 1999 and took a Kaplan review course. I then sent in the paperwork to take the NMAT in October of 1999. I took a 3 wk break after the MCAT and kept at the reviewbooks and took the NMAT. I ended up getting a 30 on the MCAT and placing in the 99th percentile on the NMAT.
Good luck and call ASAP,
Raf