My 3 month old puppy has Parvo and was given the medicine and take home treatment yesterday morning. She has a higher survival rate because she's partially vaccinated for it and was not dehydrated or malnourished. She acts like herself (i.e. hungry, drinks water frequently, playful) and not lethargic or anything like that. She's had 2 doses of her antibiotics and has not thrown up since before we took her to the vet, however, has diarrhea.

My question is, how much longer do I have to wait until she can go outside to use the bathroom? She is very smart and the 2nd day we had her; she knew she was to potty outside. When she needs to go, she whines and barks at the back door but then goes on the tile. Our lawn has not yet been treated yet because my husband and I knew she couldn't go out there anyhow so weren't in a hurry.

Does she need to have the entire bottle of antibiotics before she is immune or can she go out sooner?

Here is some information on the shedding of the virus and clean up, be sure to check out the other pages on parvo, there are quite a few helpful links.
Caring for the Recovered Dog (http://www.marvistavet.com/html/caring_for_the_recovered_dog.html)
The antibiotics don't actually have anything to do with immunity, she needs those to fight the bacterial infection.
Is your concern that she will contract the virus again or is there another dog in the household that you are concerned about?
In either case you are pretty safe if every one has been regularly and properly vaccinated.
She has had and beaten parvo developing antibodies to the disease along the way.
Make sure you follow your vets recommended vaccine schedule for her it will be very important.