Why not sleep where there is no pod around?

I think the pod people, much like today's social justice warriors, made sure there were pods around, no matter where you were--who put the pod in the health club that ended up looking like Jeff Goldblum? Who put the pods in the back yard when they were all at Donald Sutherland's place? Who put the pod in the field with the brunette (I forget her name, she was in Dead Zone as well) while Sutherland went to check on the shipping area? It seems impossible, but the pod people were clearly pushy (like today's SJWs...) and wanted to make sure everyone conformed to their species (like today's SJWs...). Sort of how math now is somehow about "race," because the pod people, er, the SJWs, make sure they're everywhere, even places they're clearly not wanted.

The pods started out the size of a finger, how are you gonna be totally sure there aren't any around?

It's also unclear what kind of a range they had. If you fell asleep 10 feet from a pod then sure you're in trouble, but what if the nearest pod is 100 feet away, or half a mile, are you safe then? SF is a geographically small place, for all we know all they had to do was dump a few million pods in Golden Gate Park, and eventually they'd take over the clueless population.