For UI demo you can use Ionic Lab to launch this project without compiled by Xcode(Ionic Lab). You can click ionic lab app,click open existed project and point to demo fold and click start server. (Better if you on internet environment due to Node.js server may have some issues under corporate).
If you want to execute on your iphone, the xcode project is under path demo/platforms/ios/sample.xcodeproj.
Let me know if you need any help.