Building an Ionic 2 project with the CLI will handle all the dependencies for you, so no you don't need to install Angular 2.
And yes you will need to know Angular 2, but you will most likely just pick that up along the way if you're learning Ionic 2 specifically.
To clarify though, Ionic 2 is not in beta, the CLI is. It isn't currently "safe" to use Ionic 2 in production apps.