Fear aggressive american bulldog puppy?

So my 7 month old puppy is fear aggressive. I've had him since 8 weeks old, and I don't really know where this came from, his worst was 4 months when he got so bad as to bark like crazy at people. Now at 7 months with a dog class and some training, he is manageable. He will let a person get within about 4 feet before he starts to growl, whereas before he would bark at people 20 ft away. I live in a very small town, which is probably why he didn't get enough socialization, because even if I take a walk downtown we are lucky if we see 2 people in the course of a 30 minute walk. But, in my small town, next week is this downtown dog festival where people take their dogs downtown and just chill. I was wondering if it would be a good idea to bring my dog. I almost don't want to for fear of him biting someone for the first time, but at the same time if I ever want him to get better I have to bring him places. Will it be too much at one time? Or will it help him to get over his aggression problems?