A sign of the times?

I came across a bunch of signs taped to trees as I was walking along the banks of the Neuse River near the back of the Bedford Community in Raleigh. It was in an area that was wedged between the river and the Neuse River Greenway and appeared to get a lot of traffic from kids. What do you think? Is this a friendly reminder or an ominous sign?

sign 1 sign 2 sign 3