Am I obligated to return to internet cafes to delete search history and cookies related to watching pornographic films, and would I apostatize if someone were to search and find what I had searched for?

You must hasten to repent from watching pornographic films and remove the traces of the sin by deleting your search history if it would lead to that sin. Do not keep the history or allow others to see pages you visited that contain absolutely blasphemous material.

It appears the questioner is suffering from misgivings (waswasah) concerning disbelief (kufr), so they should disregard them.