I started taking Oliver to PetSmart and other places after 3 sets of shots. Actually, I took him across country and even to Mexico! From 12 weeks to 16 weeks we were on a socialization mission! The vet said it was fine. I believe all of that early socialization was the best thing I could do for him. He is so easy going and easily adapts to new people and situations. I feel comfortable taking him anywhere at this point - retirement homes, parks, beach, school, store, etc. He's my little social butterfly.
Now if only I could get him to be happy calm puppy around the broom or vacuum cleaner.