"They mostly come out at night. Mostly."
Drones are now everywhere, by the thousands. Players can use them, kill them, have them kill you, etc. They have overrun the major cities and spread quickly into the wilderness and adapted to almost all terrain. Initially, there where only 100 eggs planted (by the Predators) on each of the three main continents. Unfortunately, on two of the continents, Queens somehow ended up and quickly bred, spreading their drones across the world.
Queens are not to be used in the player's stories. They are for exclusive use to Topic GMs and their storylines. If the GMs want to bring them into a story with your NPC characters, they may. But don't bring in a Queen on your own.
Chestbursters are fine...players feel free to use them whenever needed. They add lots of gore and unexpected tensions. Facehuggers are ok, but normally wouldn't be found except near pod-egg fields. Make sure there is a reason for it.
As for the pods/eggs, I don't have a problem using them or coming across them in your stories, but please get a GMs approval beforehand. Pods usually mean a Queen is nearby or they are older fields, or possibly the initial landing sites. Let the GM make the final decision on the egg-pods.
Also, for those of you wondering, the first signs of the Alien Infestion began near the end of year 42, about 4 months ago in game-terms. So that's about how long your players have been surviving on this hell-hole against the Aliens...four months.