I successfully use multiple languages in Lyx with Xetex by specifying packages and fonts in the document preamble, or using inline ERT (usepackage \fontspec etc)
I see on http://wiki.lyx.org/LyX/XeTeX, where it describes a similar setup to my own, that it says: "Note: the following steps are only necessary up to LyX 1.6.x. As of LyX 2.0, you will just need to click Document→Settings...→Fonts→Use non-TeX fonts (via XeTeX/LuaTeX). Then you can immediately View→PDF (XeTeX). " However, when I tried this out for someone I recently installed Lyx for (2.0.1 on a Mac, I use 2.0rc3 Win7) it seems that Xetex had no idea which fonts to use for Chinese (the default font was in English). Use non-Tex fonts was selected, document language package made no difference. Note the 1.6.x approach with the preamble did work. Shall I tell this user to put fontspec etc. into their preamble the way I do, should I try the xeCJK macro mentioned in the wiki.lyx xetex page, or have I missed something? Thanks, Lisa