There's one by us and my wife and I were talking about it the other day while stopped at a light...I'm not sure who the target audience for the billboard is, honestly. There's no mention of what DuckDuckGo is. In tech circles it's definitely more of a household name, but to the wider public I wouldn't expect anyone to have heard of it. The call to action is also a bit vague, and doesn't really do much for a layperson who doesn't understand the extent of the tracking, who is doing it, why it's harmful, etc.
Their original billboards from years ago apparently said "Google tracks you. We don't," which is a much clearer and at the very least positions themselves as a privacy-focused Google alternative.
(this is the billboard, for reference: https://twitter.com/DuckDuckGo/status/1266003050151411713/ph...)