If I was to take a trip to SJO and not want people to know where I was (no one on here has ever been in this situation ), is there a service that will take incoming calls from my US phone number and somehow forward them to a SJO cell? Maybe something where I could call out to the states, but my USA number shows up on the receiving caller ID?

if your usa carrier is t-mobile, their wi-fi calling will do the trick. you can log onto a wi-fi network that is connected to the internet anywhere in the world, and activate their wi-fi calling. your phone now behaves exactly as it would if it were on the cell network in the usa, in every respect. caller id, minutes used, text messaging, everything.

t-mobile is to my knowledge the only usa carrier offering this service

SR