How soon before a presidential visit does the Secret Service?

Question

start inspecting routes and facilities. For US locations? for foreign location?

Answer 1

I don't think there is any fixed amount of time.  It would depend on where the president was going, how difficult it is to secure the presidents route or the place he will be, the political climate in the country he is visiting, etc.

Answer 2

At least three days...I work security at a college campus where both the president has been as well as one of the more recent democratic candidates. I gave the tour of our facilities to the secret service three days before the event took place.