Parvo and distemper always seem to be the big scary boogeymen whenever we speak of puppies and shots. Odds are since he has only been exposed to vaccinated dogs and their yards that you're fine.
The main places I tell people to avoid with their new pups prior to vaccines is dog parks, truck/rest stops, petshops, and the vet waiting room floor (pick your pup up and carry him.)
Best of Luck!
If only it were that simple
I had puppies get parvo who were only ever exposed to my own, vaccinated dogs and were only ever in my yard, which had no previous been exposed to Parvo. When my puppies got Parvo, I researched and researched and researched. I found there are a lot of half truths and misconceptions about Parvo, even among vets!
Parvo is a very hardy virus which is transmitted through contact with infected feces. The mode of infection is through the mouth. It is not airborne, it is not transmitted though water or any other way. Given that, it sounds easy enough to avoid - just don't let your puppy eat feces right? Except that most puppies who get Parvo don't get it by chowing down on infected poop. A dog who is shedding Parvo virus in it's feces is shedding a huge amount of the virus. And it takes just a very, very tiny amount to infect a puppy. In most cases, puppies come into contact with Parvo through residual virus left from the feces of an infected dog. This residual virus can be carried into your home on shoes, on your puppy's feet or into the yard by visitors, passerby's or local wildlife. It can then be ingested through something as simple as your puppy licking his foot after walking where the residual virus was tracked. Most cleansers do not kill the virus and in ideal circumstances it can live for a very long time outdoors.
Indoors Parvo doesn't survive very long. Usually only a few weeks even if you do nothing to disinfect. Outdoors, it really depends. Freezing can inactivate it but it can become active again once there is a thaw. Heat/sunlight can be damaging to it. Excessive rain can wash it out of an area. In a dark, cool place though it has been known to survive for a year or more. The shedding period for the virus doesn't last much longer than the symptoms, although infected puppies can begin shedding the virus prior to the onset of symptoms. Once puppies have Parvo, they are immune to it. It is uncommon for Parvo to be life threatening in adult dogs, as the virus takes advantage of the undeveloped intestines of young puppies. Not all puppies who are exposed will develop Parvo though. In my litter of 6, one puppy didn't develop any symptoms and obviously had the exact same exposure.
Given all of that, it's up to you to decide if or when you are comfortable taking your puppy out and about. If she's already had a vaccine that is different than if she's totally unvaccinated. For me, I wouldn't take an unvaccinated 9 week old puppy out and about. I'd keep the puppy home and take precautions such as removing shoes before coming in and washing hands before interactions. I start taking my puppies out for socialization about a week after they receive their first vaccine. I use a high titer Parvo only or Parvo/Distemper combo. With modern vaccines, most dogs develop immunity from the initial vaccine but it takes a few days. There is a chance though that the maternal antibodies will interfere, although the new vaccines are supposed to be designed with that in mind. Some dogs never develop immunity no matter how many vaccines they are given. The only way to know for sure if your puppy has developed immunity from vaccines is to have them titered.