Agents have recently been notified by our Association of Realtors that Florida state law does not allow any signs to be placed in the right of way (which, of course, is where most signs ARE placed). We've been notified that the local governments will be taking the signs, and also issuing fines. They add, we CAN put signs on private property, and remind us that this must be with the permission of the owner.
This takes me back to when I was first in real estate, when I would always knock on the door of the corner homes where I wanted to place directional signs and ask if they would give me permission. Some, in a neighborhood I farmed and help frequent opens, would say - sure, and in the future you don't need to ask (bother me?), just put it there. If they say no? then try other neighbors across the street. (It's also nice to send them a nice thank you note the next day).
A realtor-owner of two highrise condominium units that I recently listed here in downtown St Petersburg, Florida, was planning to hold an Open House on his units. When he checked with the condo association, they would not allow a sign on the condo property and suggested that he just put the sign in the right of way. When he called me with this "good news" I pointed out that this was illegal, and suggested that he park his car in front of the condo tower and put his Open House directional sign on his car, not touching the ground. He even improved on that - he opened the sun room on top of his Mercedes, and had the Open House sign sticking out of that, on top of his car.

Ohhhhhhhh that's good!
And to think I wasn't going to get the sunroof on my new car....
It is a sad state of affairs when our sellers are limited by sign laws. I think this has come about because of careless agents leaving signs around long after the property has sold.
We have areas in Metro Denver where you have to "register" your open house signs. I learned this the hard way one day when I planned to do an open house, but was told my signs needed to be "registered".
Of course the licensing office was only open during the week, so that week was lost! My sellers, the town tax payers were the ones that were hurt.
I'm not a fan of open houses, but in some cases they do work. Having laws that prevent us from the normal course of business is interference that should not exist.