I have a PhoneGap app run on Android/ARM platform fine. Does it work on Android/Intel platform without modification? No NDK was used.
Yes, your Android app should work just fine on Intel-based Android devices. If you'd like to test it to be sure, we have set up a partnership with the device testing service AppThwack, where you can upload your app and have it run/test on actual Intel-based Android hardware, all for free. You can find more information here:
You could also test it on an Intel Atom-based Android Virtual Device in the Android SDK emulator. The images are available from within the SDK manager (including a newly released image that includes the Google APIs). Don't forget to get and install the HAXM hardware acceleration driver for the emulator, which speeds it up dramatically, and makes testing in the emulator much more pleasant.
If you run into any issues or have any questions, let us know, and we'll help you out. Good luck! :-)