I'd suggest you also take a look at the Gold Coast (last one on Carang's list). It pretty much meets all your criteria and there are a fair few expats too. It's a 30-45 min bus ride (resident's bus) into Central each morning and back int he evenings, close to hiking and beaches, has excellent gym and pool and tennis and squash, appts are on the larger side and much cheaper than those closer in, good restaurants in the shopping mall (5 minute walk) as well as a decent super market and chemist.
There is also horse riding in Tuen Mun which is about 15 mins away by bus.
You can google "hong Kong gold coast" and find the official site which has the bus timetables etc; please read everything on that site with a pinch of salt - they really like to show unrealistic pictures (the photos are photoshopped - it's nice but not THAT nice) but it gives you an idea anyway.
Then yes, like the others, I agree - come and get a serviced appt for a while and make a choice. The Royal View in Tsuan Wan is not bad for a month in a serviced appt (particularly if you are thinking about GC area, as it is not too far away and you won't get too used to the convenience of being right in Central!).