Any car signs that have adhesive are completely car wash-safe, with the exception of EZ-Stick Vinyl. This includes car wraps, car door decals, car lettering, and rear window graphics. These products are printed with solvent inks that embed into the material and are UV- and weather-resistant.
EZ-Stick Vinyl decals, even those with the Outdoor option, should be removed before washing the vehicle as hard pressure against the material could remove the ink.
Non-adhesive car signs (i.e. car magnets) must be removed before entering a car wash, as the brushes will pull them off your vehicle.