Until recently, a 'wifi bridge kit' has been the connectivity of choice for LED sign owners.  The setup is simple; a wireless antenna is mounted on the sign, and a paired or mate antenna is mounted on the sign owner's nearby building and connected to their network.  These antenna's only connect to each other using an encrypted password.  With a clear line of sight, the antennas can communicate beyond 1 mile.  The sign is now completely connected to the local network and internet just as if it were plugged directly into a router.