Try it out, if someone is motivated enough and you have their solution, all they will care about is their situation. Just make sure you can read it from a good distance. I have seen signs where the letters are so thin from a basic marker, makes it appear like nothing is even on the sign.
I've seen several friends successful with both strategies. If people are motivated I don't really think it matters much. Give it a try and see how it goes! I think that they need to be positioned in the right area that you are trying to buy in. Most of the time these are put at 4 way stops. Also, make sure you aren't going to be receiving any fines in your area for putting them out. Best of luck!
Take a look at your city code. Search "Your City Sign Ordinance" or call and ask about the rules.