[Jen2010]

Definitely stop taking him to the dog parks. 3GSD4IPO is right in that some dogs just don't really like other dogs. Taking him out of those situations is best so it can't escalate to something worse (like a bite). So yes, moving across the street to avoid other people/dogs is a good idea. I have to do the same thing with one of my dogs. Treat him and praise him too.

You might want to look into hiring a positive-based dog behaviourist.