Does this garage generally fill up at noon on a week day? I'm attending an event at the Waterfront Hotel on Thursday, noon.

No the garage never totally ever gets full except on the weekend when there is an event

I arrive at the parking lot at 6:20 am for work. Typically, the lot is empty at that hour. Sorry I have no idea what is going on in the parking lot between 6:20 am and 5 pm. There is ample free street parking within walking distance, of the hotel, near the parking lot.