In case anyone else runs into this issue of the Range slider not working with side menu, the fix was covered in an existing issue as described at https://github.com/driftyco/ionic/issues/318. The cause was the sidemenu's event handling interfering with the slider.
It sounds like the fix will be pulled into a future Ionic release and in the meantime there are two different fixes at https://github.com/driftyco/ionic/issues/318. I found the directive workaround by ArTiSTiX worked well - it's described at http://play.ionic.io/app/f44b3d0adee8).