I need some clarification

I use 0 mph - because I want the alert in all cases even when I am below the speed limit.

It's not a dumb question, but the answer is "It depends."

I have my speed alerts set for the speed limit of that location. This means, however, that it will alert the entire time if I'm going over that set speed.

Some people have indicated that for a 25 mph speed alert they don't want to be alerted unless they are going 30 mph. The only way to do that is to set the alert for 30 mph. Be advised, however, that that's what will come up in the red alert bar.

So, set them for what works for you, just know that if you are traveling above the set speed, it will alert the whole time you are in the alert area.

ok... but if you put 55mph, but you are driving through a speed trap with a 45mph limit, will the GPS alert you to the fact that you are in a speed zone?

Yes, you will get an initial audible alert (either a double "bong" or a custom audio alert if you have one loaded) that you are entering an alert area.

Then, the red alert bar will stay up at the top of the screen for the duration of the alert area, but if you are under the set speed, you won't get anymore audible alerts.

If you go above the set speed, you will get audible alerts in a addition to the visual red bar.