I'm sure garlic is ok, but yes probably in large quantities not. Rachel Ray used to cook for her dog and garlic was in quite a bit of the food she made. She used onion juice (grated onion) as well b/c the dog didn't like it, but it didn't seem to be harming her. My best advice is to just ASK...
We have a walnut tree in our yard and the walnuts get EVERYWHERE, especially b/c of the squirrels. Our new puppy just started chewing on the old nuts from last year and she started puking this morning. Could it be possible that walnuts are bad?! We are going to the vet this morning anyway, so...