using a leash is the only 100% certain way to keep a dog out of the street.
The way you have described your neighborhood, I would never consider letting my dog off-leash. Too many things going on and too many dangers.
Actually, it isn't, not with a flat collar. The dog can slip a flat collar and then its off into the street it goes.
You should use a martingale -- no-slip collar on the puppy. And a leash. At the same time, work on recall, and an Emergency DOWN. These can save a life if something happens and the leash comes out of your hands.
The trick is to NEVER make it optional. Give the COME command ONLY if you can enforce it. Enforce it every single time. Say it one time, if the dog does not come, a little tug, if that doesn't get the dog coming, than real your leash in while walking to your dog. Then walk your dog to where you were originally, and then say Good Come. Also, NEVER, EVER yell at or punish your dog in any way after you called it and it came. Don't find a mess in the living room, call the puppy, and then berate it. No!!! Coming to you is the best thing in the world. Always praise him when he comes.
When he comes have him sit in front of you. COME FRONT. Pet his head and take and release his collar, regularly. Get him used to this while you praise him. In a fix, leash breaks, whatever, you want to be able to get a handle on that collar.
The umbilical cord is important but to make them safer, teach them these basic commands. Hopefully you will never need it, but if you do, it will be there.