For Exterior Signs , Yes . Definitely . And even most of the interior signs.  Not only you need a Licensed Contractor , Also your contractor must be bonded and insured as well. Please make sure to ask for a certificate of Insurance and ask them to  ad you as an additional insured. Sign works may sound simple and easy but many people have lost their lives in this industry. Sign makers and Installers work with electricity , They go inside attics and work in heights. Not only your Contractor must be Licensed and insured , but he must have trained and experienced employees. " DO NOT HIRE A SIGN MAN BEFORE YOU SEE HIS LICENSE , WORKERS COMPENSATION INSURANCE , & LIABILITY INSURANCE".