I agree with Susan here. If your dog is vacinated, you should be good to go. Dogs love spending time with people, but would rather be with other dogs. There is a lot of joy in watching your dog run and play. Nothing and I mean nothing can tire out a dog like another dog.
One thing to be wary of is to make sure you have your pet vaccinated for Kennel Cough. That is the only thing my dogs managed to pick up from the park.
If you are worried about them "bringing home diseaese" remember that a lot of animals poop all over the ground and no one picks it up. Just wipe your dogs feet and rinse it off if they get really dirty. Wash no more than weekly using non-perfumed gentle dog soap.
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If only closed minds came with closed mouths.