If I had a puppy...I wouldn't let an unvaccinated dog come by. But at this point...I could care less. My dogs, after 3 and 4 years of life are probably immune to most things that a dog could bring in, so I don't worry.
A puppy...I'd try to hold off for a while even after the vaccines. Remember, the vaccines are against diseases that can possibly kill your dog, but there are hundreds of other things our dogs can get that will cause you to rush to a vet or leave your dog under the weather for a few days.