okay, i woke up early this morning specifically to tackle the kitteh infestation in metropolis and it really wasn't was bad as i was afraid it was going to be...certainly not as bad as hunting down the pigeons in gta4.
anyways, i didn't start this until about 65% through the game, and i was going to wait until the end of the game because of how everyone was saying they kept triggering fight with the generic goons as they searched for the cats....however, i am certain that the best part to do the cat searching is when the little white icon with a red question mark in it pops up (usually above the daily planet) because when that icon is there, there will be NO other icons or random encounters...problem solved. as long as you do not approach the question mark icon, you are free to roam around and find all the cats.
it took me about two hours and i got em all in one easy go using this method.
also, a tip about navigating the map to find the cats....use the road lines on the little map on your HUD to help keep your bearings and get from cat to cat a little bit easier.
Wanna see what the bottom of your avatar's shoe looks like?