Ghettoisation(is that the word) helps to delay the integration process.The non Ghetto lifestyle does not necessarily speed up integration. Having lived and worked as an expat (we never thought of our selves as immigrants)I can assure you westerners very quickly develop ghettos when in host countries

Agree—it's natural to coalesce in familiar 'safe' groups (we're more or less hard wired to do this)... ...I suspect it's the second generation who make the big difference—they naturally mix with their age group peers (& learn the language more easily, too!)