sai kung is in the new territories. it is not in the middle of the hub-bub of hk. it has beaches, hiking, a friendly expat & local community, decent local schools, ESF schools and a few "international" kindergartens as well as good local kindergartens. there are quite a few restaurants, thai, pizza, chinese, american, sri lankan etc.
to get to 'the city', you can either drive (45 minutes from my door to central) or take the minibus/double decker bus to an mtr station and then train from there. you can either go to hang hau station or to wu kai sha station.
there are minibuses/double deckers to: mongkok, hang hau, choi hung, kowloon bay, causeway bay (only a few per day), kwun tong, shatin, ma on shan, diamond hill.
it's not the life for everyone, but if you like a laid back lifestyle, where you can get to know your neighbours, it may be for you.
sai kung has a good mix of locals and expats.
we, personally, live WAYYYYY out in the boonies(hence the extraordinarily low rent), but you could easily get a beautiful, new 2100' house with a garden and a car park for your budget. you'd probably still have $15-20k spare~ the house immediately in front of us is vacant, has been completely redone and they are asking $25k if memory serves. we are about 15 minutes drive from sai kung town itself. but our village is 90% expat.