Off the interstate, temporary (e.g. "sandwich board") signs can be put up two weeks before the event and must be taken down by three days after the event. They should be off the shoulder of the road and you should get the permission of the owner of the adjoining property before putting them up.
Some additional info, that might be useful in the larger context of ALL EVENTS in CORTLAND:
On the Interstate, there IS a program of posting information about GAS, CAMPING, LODGING, FOOD and ATTRACTIONS. But these are usually either permanent or seasonal businesses. I talked with him about the possibility of using an ATTRACTIONS sign to give info about temporary events. This might be worth thinking about if we have:
1) More people interested in having their "attraction" advertised, to spread out the cost. (e.g. Country Music Park, 1890 House, Lime Hollow...)
2) We have a number of different events during the year in the Courthouse Park, since additional (required) signs would point to the park, and should be covered when not needed (as for a seasonal business).
Here is the deal (more or less). Someone needs to request a permit from the DOT for the sign backing board. That person (business) has to pay for the sign (est. cost about $7,000 for a 6 panel board, probably $5000 for a 3 panel board). Other businesses can get a panel on the board by paying the proportional fraction of the original cost (plus the cost of the panel itself ~$400) to whoever put the board up.
In addition to the big sign on the Interstate, you need to provide signs on the exit ramp (~$200 each), and signs on each major intersection between the exit and the attraction.
Once the signs are up and paid for, there is an annual registration fee.