I wouldn't take him to the dog park. I used to take my GSD when he was younger and he was fine around other dogs and seemed to enjoy himself but other dogs have behavior issues and health issues and some dogs have no business being around other dogs. All it takes is for one bad experience and your puppy could become fearful or aggressive towards other dogs.
I would enroll in a puppy class so that you can socialize him with other puppies or I would find some nice people in your neighborhood with well behaved dogs or friends or family members with dogs and have play dates with them.
Sinister "The Prince of Darkness" 4 yr old black male GSD 3.11.09
Draco "Dakota's Unbreakable Vow" 5.5 mth old male Dalmatian 6.30.13
Cats: Chaos, Mayhem, Monster, Wicked