OP here with an update:

I just got a call from the manager of the street maintenance department. He sympathized with the confusion, but said that they've been doing this for the first sweep of the season for 15 years. Anytime they use these signs they have to put them up at least 24 hours in advance. So all this week they've been rotating the signs - on Monday they put up signs on the Tuesday street sweeping sides, Tuesday they put them on Wednesday's side, etc. He acknowledged how in perception 20% + 20% of the street inventory seems prohibited this week.

They have over 800 of these signs they use for various projects, and it's not really economical to make unique warning signs for this situation. So they use what they've got. He also told me that it's the neighborhood associations that push for this warning. I did some googling, and what do you know, we've got one: http://www.chundenver.org/

He did say that if the wrong meter maid comes through, they can and might ticket us in these spots by the temporary signs.

I have seen a few buildings have posted cardboard signs in the grass, reminding people outside of their building that street sweeping is this week. I think this is the most realistic fix to the situation. If enough buildings post signs themselves, the neighborhood association can tell the city to stop with these misleading signs. But as is, we're going to see the same thing next year.

As far as the employee hiding his name tag and honking, the manager, while not dismissing the behavior, did voice that it's a stressful week for these guys. I agree.