Permits depend on local city requirements.  I would go to local building permits office and ask them.  Most likely not needed, but maybe if you put orange safety cones to close sidewalk it may be needed.  Main thing is you have to account for water run off, as it can not go down the storm drain or there may be fines.  You may be able to sweep/blow  water along sidewalk to dry or wet vacuum and dispose down sanitary sewer.  Best to check local requirements.  Thats maybe a two hour job tops, so start early and be done spraying by 7 AM.