I, like many others often avoid caches where muggle activity is high, especially in playgrounds. I would be on the phone to authorities too if a saw a 40 ish year old man acting suspiciously in the bushes while kids are on the swings.
One trick I sometimes use, which is ironic if you think about it, is to wear a high visibility ( usually fluorescent orange or yellow ) vest while doing caches next to roads and the like. The vest is designed to make you visible to traffic etc, but has the effect of making you invisible to everyone else.