fifa - 5 expat kids really isn't much. Asian expat kids are more common than Caucasian ones in ACS, I think. (Not talking about Asian scholars - that's a different matter.) Japanese kids are certainly rare still.]
Besides ACS(I) and MGS, I think RI, RGS, SCGS and Cedar Girls' are also good fits for expat kids. I'm not so sure about TCHS, NYGH, Catholic High and others - those are still quite chinese-y though they certainly have significant English-oriented populations. Then there're the top-ranked 'neighbourhood' schools like Anderson, BPGHS etc. - not sure how those are.
I really wonder how many Western expat kids have ever gone through JC. Must be pretty few.