My vets always told me that after 2 of the puppy series of shots it was safe to take the puppy around to see people and tolerant, sweet dogs that were healthy. I'd stay clear of places where tons of dogs hung out, like dog parks or pet stores until a little later. But it's very important to get them socialized...meeting new people every day, seeing different environments, different ground surfaces, differently clothed people, people carrying things...large packages, umbrellas, wearing hats, people with big coats on, without big coats on etc etc etc. All these things need to happen without over whelming the puppy, which means over time. Well, you don't have a lot of time so it's a balancing act to be sure. You need to make sure your puppy has happy experiences, not frightening ones when you introduce him to new people, places and things. Associate those things with yummy, tiny treats and happy times. He needs to have a pretty good supply of all this by the time he's 14-16 weeks of age or he'll never regain that and it can make a serious problem, every bit as serious as parvo. A dog that misses out on that early critical socialization period between birth and about 12-16 weeks of age will likely be very mal-adjusted, frightened, unbalanced and it is extremely, if not impossible to regain any of that lost time.
That window of time is there in nature in all animals, designed for survival and the perpetuation of the species. If a dog has gotten along fine all this time without seeing an umbrella open or a loud machine, certain kinds of people or animals, he figures it's not necessary in life and will forever avoid that thing and may well be afraid of it. It has gone into the unsafe/unnecessary/to-be-avoided "folder," while the things that he's enjoyed seeing and gotten use to go in the safe/part-of-life "folder." If this were not the case, you'd have deer and bunnies coming right up to you in the forest, unafraid and wanting to make friends. So, it's of the most monumental importance to socialize your puppy systematically, every day and forever. You will be able to lighten up after the puppy is older. But now...every day. If you don't train your puppy anything else, carry out this important socialization.
Another thing you can do is ask around of different vets if they have seen a lot of parvo lately in the area. If that's the case, you can take more precautions, like take him around in a stroller. But I wouldn't recommend that unless the situation requires it. It is good for them to see things from their own perspective, height, feel the ground, smell the scents and so on.
It's the way it is that the puppy vaccines and that critical period of socialization conflict time wise. But people who put off socialization until all the vaccines are finished miss that window and it's a lot harder and oftentimes they'll have life long problems with their dogs. It's work...you have to be disciplined to get out there with the pup, think about where you're going, even make a check list so you cover as much as you can without over whelming or frightening the puppy in his encounters. Executed well, it will pay off in the end. Good luck.
