Stickers on Signages in Baguio City: Vandalism or Art?

Should the city of Baguio allow the posting of stickers on signages within the city? The two signages in these photos are along Session Road. One is beside Skyworld and it's known as a tourist hotspot on its own because it's probably the most photographed signage in the city. The other signage is near the stairs going up to the main entrance of the Baguio Cathedral.

Both are often covered with stickers from vloggers, content creators, businesses, organizations, travel organizers, religious groups, etc. 

These are also often cleaned up by the city but it's just a matter of time before they're once again covered with stickers. The signage beside Skyworld has been recently cleaned as evidenced by the white residue left behind. But someone has already posted stickers with what looks like Hebrew writings on them. Who knows what these writings mean.

Some defend the posting of stickers on these signages as a form of expression. Harmless and can be considered artful, they say. 

What do you think? Should this be allowed? Or should it be prohibited?