The locals are gonna be so shocked and confused. He should definitely do this. As an FYI, in terms of world consequences, if he destroys fountains on personal property, the owners will likely be displeased. Little will come of this except that Percy might notice side-eyes from a handful of people, should you want to include that conflict in a future thread. The Queen may eventually have a word with him about destroying public property, but he'll realize very quickly that she (and her Court) isn't displeased because the destruction was for a good cause.

He sure can wreak havoc.

The river is probably about half a mile from the pavilion at the center of Old Town.