I would assume this would fall under the same rules as wearing Masonic jewelry and displaying car emblems and so on. I think one should wait until they are a MM. I could be wrong.
I would say they should probably wait. You shouldn't wear S&C jewelry, hats, shirts etc., your car also probably shouldn't wear them.
I would definitely wait until you've taken your third step. You'll appreciate it more. But surely no light wearing until you become a MM.
Supposedly shows the current Masonic plates for the different states. http://www.daylightlodge.org/licenseplates.htm
Interesting site (where the various states are shown). To all you masons, who do not yet have them, you need to get with your state legislators, and demand the tags. I initiated the legislation to get the Masonic plates in KY. You will notice that Arkansas has a Masonic plate. Members of the Grand Lodge of Arkansas (F&AM), cannot purchase these tags. The tag was designed by the MWPHGL of Arkansas, and a portion of the purchase price, goes to PH affiliated charities. How sad.
Not sure about the quality of the source , but; http://burningtaper.blogspot.com/2010/02/arkansas-masons-forbidden-from-buying.html