He would have to travel and sneak the muggle way, it seemed. Winter had already grown to the size of an adult horse, but he was still too small for flying. If Jon was as big as a small child, he'd be able to mount his dragon, but he was nearly 6'3 feet tall and very heavy. The dragons themselves were still acting like small hatchlings from time to time and were unused to their quickly increasing size. Even though they were intelligent, the process of growing up mentally took time and experience they did not have. Staying any further at the Wall, where their growth was greatly accelerated, would only do them a disservice in the long run.