Candidates running for the office of city clerk petitioned the city manager to hang political posters on city stop signs, lamp posts, and utility poles to promote their election but discovered that a city ordinance prohibited the positing of signs on public property. The city manager stated that posting signs on public property was not allowed because they detracted from the main purpose of the ordinance, which was to improve the appearance of the entire city. The manager suggested other ways to promote their candidacy that did not violate the city ordinance. The candidates claimed, however, that this city ordinance was unconstitutional because it violated their rights to free speech. How would you decide this case?