While I don't know as much about you as reflection - If you're in a relationship already, going to meet a guy that you met online is a big no-no, unless of course your significant other is invited as well and you're looking for friends.

However, that doesn't seem to be the case.

It's possible that he's mentioned marriage simply to get your take on it. He may not want to "waste your time" so to speak by starting a relationship with you if you've already made your mind up that you're not ever getting married. He may just want to know that it could be in the works at a later date Y'know? Still that is pretty odd - discussing marriage after only a few days of meeting. Don't be afraid to ask him about that if you feel the need.

Either way, if you choose to meet this person, meet him in a public area. Let your friends & family know where you're going and when as well as when you may be expected back.

Who knows, it may be a decision that changes your life altogether.