I'm no lawyer (unlike the man who created these signs), but it seems to me that the notion of implied consent would render such signs moot.
When anyone drives on a public roadway in any state, the implication is that they consent to the rules of the road, which includes taking a sobriety test if officers have deemed it necessary. DUI checkpoints are often set up during times when police reasonably assume that a large number of drunken drivers might be on the road, such as on weekend nights during big events.
Personally, I have no problem with this. Intoxicated drivers imperil us all, and everyone is aware of the dangers of engaging in drunken driving. I don't find it a victory for "freedom" when people get wind of where a checkpoint might be (though if that information deters someone from driving, it might be useful).
I also don't see the virtue in not cooperating. I've been through several checkpoints — including one that was set up near my home one night, which I turned just in front of to go to the store, hoping that the officers wouldn't take that as a sign I was avoiding them (I wasn't; I was stone sober and straight from work). All these times, it never occurred to me not to cooperate (then again, I was always sober), and I have a hard time understanding why someone with nothing to hide wouldn't. (Again, we're talking about the public roadways. I might feel differently in other situations.)
So I know checkpoints are a hassle. I know that like with anything law enforcement-related, there is potential for abuse. But all in all, I think checkpoints are an asset.
Traffic can be a dangerous proposition — drinking, gabbing, texting, fatigue, car trouble, general distraction — and the mistakes others make can be life-altering or fatal to themselves and to others. Because of this, I support the fair enforcement of traffic laws. Not abuse, mind you, but neither will I equate "freedom" with the "right" to avoid responsibility.
I hope everyone who shares the road with me feels the same way.