A boy and a girl stand in a median amongst Mike Huckabee signs.
Two people stand on a median with advertising signs.
A boy and a girl are two people, Mike Huckabee signs are a specific type of advertising signs, this is a simpler rephrasing.
A boy and a girl are two people.   A Mike Huckabee signs are advertising signs.
Mike Huckabee signs are advertising signs and a boy and girl are two people.