Well, if in a 24 hour period, the ammonia returns to 0, and the nitrites are 0, then you have enough of each bacteria to handle new fish. If it doesn't drop to 0, well, keep feeding ammonia to the tank to get it up to 5 ppm until the bacteria have grown to the point where they can process all the ammonia in a day.
Leaving the tank for about a week may have killed off some of the bacteria, but I don't think it should take you all that long to get your bacteria back to where they should be.
Hope this helps.