Yes, if you sign in Intel XDK then that's all you need. You can submit to Google Play just like that. I'm not 100% sure if that's an issue for you or not (it would be if you previously built with a different system, like CocoonJS).
To disable signing, go to your build settings in Intel XDK (click Projects at the top-left, then select your game/app), select Android-Crosswalk, then scroll down to a checkbox that says "Signed". Uncheck that.