I don't think it is possible to be ANYWHERE in HKG and not get a wifi signal, in most areas there are 20-30 signals that show up at any given time. Skype wifi allows you to connect to almost ANY of those signals for pennies a minute. Same in SIN, PVG and a lot of other cities. You simply fire up the wifi, look at any of the signals you are getting, select it, and it will tell you the per minute rate - if you like it just hit connect. And that's not just for phone calls, you are connected to the internet so you can use skype, and any of your data programs like maps, around me, email, etc...

As far as using local sims, that works good for local calls, and from what I understand a lot of folks have a google voice account with their home number forwarded to whatever their intl sim number is. I have not tried it but a lot of folks say it works great.