Yes, get the ammonia.
This is what I'd do (I do the same when I set up new tanks); add enough ammonia to give a reading of 1 or 2 ppm. Add some mature media from your friend's filter, and leave the tank running overnight. If, when you test the next morning, there is no trace of either ammonia or nitrite, then you're ok to go and get fish.
That way you know, for certain, that the bacteria are alive and well and doing their job.
If there is any reading at all for ammonia or nitrite, then you have to add more ammonia and test again in 12 hours, as you obviously don't have enough bacteria to give you a properly cycled filter.