It should be possible to meet one of the moonwalkers, provided you know well in advance where they'll be.
Armstrong is never available anyway.
Aldrin is very much willing BUT it's very expensive to invite him!!!
Bean signs autographs for collectors but he doesn't really speak very very much.
Mitchell goes to Quantum computation theories convetions and is also very hard to meet.
Scott...I don't know; I don't think he goes out that often; but I'd LOVE to chat with him!
Young is still working for NASA, he'd go wherever NASA asks him to go but he's very inaccessible and not talkative.
Duke might be very interesting (though, more so if you are a believer).
Schmitt isn't traveling too much but when he does, it's because he was proposed with a large pay check. (He did answer a question I asked on the internet, once.
Cernan: I'd love to see and talk to him too; he's the most eloquent of all

Raoul