Hm, I decided after some fiddling that it was better to have spawn points placed around the map, I have it spawn npc's every 1 second if a random variable = 1, otherwise not. When npc's are offscreen they are destroyed.
I'm still struggling with having the game check where things are, I need to fix a zone where the spawn rule applies but I just can't figure it out. I feel like it's super easy to do, I'm just not seeing it...
And, I can't figure out how to check for current position either...