Oscar, who cares, north or south. He says 4 degrees from equator. It puts equivalent to Northern Malaysia. I researched this topic when I was looking for a land. I was trying to find examples of durian orchards in Peninsular Malaysia above 800 meters, but to my knowledge there are none. Its simply too high. Yes, it contradicts Soren, but 4 degrees in latitude and couple hundred meters difference in elevation could make a difference whether you have ornamental or a fruiting tree. If you go by Julia Morton's text it says: "The durian is ultra-tropical and cannot be grown above an altitude of 2,000 ft (600 m) in Ceylon; 2,300 ft (700 m) in the Philippines, 2,600 ft (800 m) in Malaysia" Its not really accurate because I personally seen 7 year old durian tree in Ceylon at 825 meters. I checked my altimeter when I saw the tree. I did not expect it to be right up there with highland tea.
I think it will fruit at the place you provided, but I'm not convinced 100%. To be safe try to come down to 500-600 meter range. I also believe this will positively influence your "years to first fruit" and productivity.
Try lean towards safe side as much as possible. Latitudes and altitudes are just for reference and sort of guidance. Individual places at the same raw data points might be radically different. There are many influencing factors. For example there is a town in Mexico, officially south of tropic of cancer at 22 north where time after time they get temps well below similar latitudes, and they even had snow at sea level!!!
As far as watches my observation that they are pretty accurate. Maybe 15-20 meters error. Enter "altimeter watch" into ebay search, and you got plenty of choices. I think Suunto is a premium brand consistently above $200, but there are also cheaper alternatives like this one
http://www.ebay.com/itm/La-Crosse-XG-55-Watch-Altimeter-Compass-Barometer-XG55-/390837469580?pt=Wristwatches&hash=item5affba818c Can't vouch for performance. As Oscar says: recheck with Google Earth. Software is accurate.