(I'm not a lawyer, but I've looked into this some.) You can place signs on your private property, with two exceptions: 1) if your neighborhood has an association or covenant barring the placement of such signs, or 2) your municipality considers X feet from the street/road to be an easement or "public right of way", in which case you simply place your sign more than X feet from the street/road.
Now to take a quick detour here, I don't believe, personally, a neighborhood rule against signs should be considered unconstitutional provided it is part of a covenant you agreed to when you bought the property. A deal's a deal. Also, I personally don't think the Constitution enters into it since the Constitution defines the limited powers of the Federal government and lists some explicit limitations thereof. The modern idea that the bill of rights applies to the states is part of what's called "incorporation doctrine", which is a result of the 14th amendment. But the wording of the 14th seems to be a pretty shaky foundation for such a doctrine in my humble opinion. Besides, for some of the amendments in the Bill of Rights to even make sense as applied to the states, they would have to be re-worded.
Okay, sorry, I got a bit side-tracked there.