This breed is documented as friendly, gentle and patient, rated 4 out of 5 with other dogs and 4 out of 5 with strangers, and a maximum 5 out of 5 with children. Those ratings describe an intention, not a skill. At 150 pounds, an enthusiastic greeting is a physical event regardless of how kind the dog means it to be, and a friendly giant with no recall is harder to manage in public than a wary small dog with excellent manners.
So the honest use of a very large park with an off-leash area is socialisation and reliability under distraction: teaching a young giant to be calm around other dogs, to disengage, and to come back when called while something interesting is happening. That is a training project with a defined end, not a daily mileage requirement.
Memphis makes that project unusually affordable. Group obedience classes here price well under the national average, because training is a labour-based service in a low-wage market. Trainability in this breed is a middling 3 out of 5 — responsive to consistency, not automatic — which means the classes matter and the timing matters more. Everything is easier while the dog can still be physically managed.