Yeah, that far parking lot is pretty large, eve with the restaurant packed it doesn't get full.
It is well worth staying for sunset as well, it is probably the only time the place is quiet Most folks to shut up and stare, then they ring a bell to declare the sun 'down' and the place goes back to its noisy self.
How do I know this? I came to Austin as a tourist 13 or 14 years ago, some things don't change.