Actually...right now is the perfect time to solve this. Avoiding the problem is not always the best solution, and at the moment your problem isn't that huge.
You have to show the dog that its YOUR choice when and with who you choose to interact and its not his decision to drive other dogs away from you...especially friendly dogs.
Since he's currently not being extremely aggressive, you can correct this behavior. Just don't allow him to chase away the other dog. Put him on lead, make him sit, and pet the other dog, then pet him, then pet both at the same time. If he tries to go at the other dog, correct him. If he tries to get in between you and the other dog, correct him and put him in a sit or a down next to you while you pet the other dog.
Start out slow, and only do this for a second or two with a dog you're noticing your dog is having problems with. Of course after a few pets, reward your dog with something of high value to him.