Should I add the students I meet briefly abroad on Facebook? I would rather not.?

[K]

I'm doing a short-term study abroad program with some other students from my high school. We have been attending the local spanish-speaking high school, and have met many different students. They have been asking for our Facebook and I now have a lot of requests from these people I don't know. I'm very strict about who I add on Facebook and I never add people I don't know, so I would rather not add them. However, I don't want to be offensive (we are also switching to another school next week, so I wouldn't see them again after that).
Would it be better to add them and then delete them after I return to the States? I just don't want them looking through all my past stuff, even though none of it bad.
Gracias.