Multi touch is supported by default, but I think I remember something like the android browser not being able to handle it.
If you have something like "on touch" move the player and "on fire button touched" fire, both should work as intended, in multi touch.
If the browser can't handle it, not much to be done there but rethink the controls.
In this page of tutorial:
here are two known issues when using PhoneGap:
- Android 2.x does not support multi-touch properly. Android 4 (Ice Cream Sandwich) fixes this.
So here it is, solution is to use android 4.