There's no regular bus that way - I don't think (but don't know for sure) the monastery bus goes that way.
You could walk if you're one of those keen people who walk all round and sing as they go (Fal de reeee, Fal de raaaaaa etc). There's another good place up there too, Platanos, which is the one we go to. View doesn't quite match the Panorama one if you care to airport watch, but a lovely view nevertheless. The only time we ever went to Panorama, it was raining stair rods and the car park resembled a venue for bog snorkelling, so we drove out again and went to Platanos - enjoyed that so much that we go there every year now.
You will also see quite a few times in the forum (and elsewhere) that if you book a meal there, they will actually come and fetch you, then take you back. I have no idea how they can make a profit doing that.