making signs look real, as if they were supposed to be saying something is much more effective.
match the letters and colors
make stickers at home, and stick em along trips being already made.
i don't think a McDonalds is a good thing to have out for children
i would much rather have my kids see the word fuck everywhere than see ronald mcdonald tricking them into eating shitty food.
personally
i get premade bumper stickers, white/blank
i cut out a stencil for the sticker i want
place the stencil over the sticker and spray with correct color spray paint to match the sign you plan on putting them on to match.
"some people" have done this
STOP
BUSH
works good on a stop sign...