With Memorial Day upon us, the coming weeks will be New Jersey’s first big test on whether its brand-new legal weed industry will have enough marijuana to meet what experts predict will be a big summertime demand. Carlos Hernandez, a valet at the Shore, can already see the crowds returning as he parked cars all day and night on Thursday at a Ventnor high-rise that overlooks the ocean. “The vibe is real good,” said Hernandez, 47, of Pleasantville. “I have a lot of friends who go to all the dispensaries to buy weed and they’re extremely happy that they don’t have to go to jail for it.” But suppl…