There does seem to be enclaves and I can only comment on those I have heard of / visited.
Bukit Timah, Holland Village, River Valley, Tanglin, East Coast are just some of the areas that are popular with expats. What we found (and our last locale was Sydney, Manly) is that where you live will depend on some of these factors i) budget ii) commute/place of work/school iii) desire to work to certain amenities or not, iv) facilities v) if you will have a car.
We live in a condo
in River Valley. This is approx. 2-3kms from the city, walking distance to going out hubs but a drive to beach and key parks. Because it's close to the city good condos
and certainly houses cost more / or you get less than if you go further out.
When we first arrived, we were driven around by an agent to check out different areas. This is something I highly recommend. For us, we wanted a short commute to work (10 mins) and ability to walk places rather than drive. We have also found our condo - called Aspen Heights - to be fantastically international and friendly. As a first move I do recommend the right condo for meeting people. I say' right condo' because I heard from friends that their aren't like ours. Having now racked up a year, I would prefer a house - even a small one - to get the outdoor space for the kids.
Having said that, poring over the expats papers you should quickly be able to amass the key social activities in your area and meet people through these...and therefore a house will be fine to start.
You do tend to get more for your money on the east coast vs holland or bukit timah or river valley for that matter. Go and see several areas.
Leases tend to be 2 years but because of the rental slow down you should be able to i) get a substantial discount on the advertised price (I seriously suggest offering 25% less as a starting point) and ii) negotiate a year term so you can then mix it up if you want a change. Also I can't recommend enough that your contract has a diplomatic clause that allows you to get out after 14 months (if you have a 2 year lease). Leases are watertight and if you job situation changes and you have to leave you don't want to have to pay it out for the remainder of the lease term.