There's no such thing as a checkpoint. Police have no authority to check anything.
Vegas? I'm thinking Sparks P.D. might cancel theirs, as they cancelled their December roadblock.
If you are going to make signs, make something luminescent. None of the home-made signs (or even the thug roadblock signs) can be read from a respectable distance, until the headlights are right on them.
Also, I was thinking of better wording.
GANG ACTIVITY AHEAD: TURN RIGHT NOW! Then, for the people who missed the turn.... WINDOWS UP/DOORS LOCKED. DO NOT ANSWER QUESTIONS!