When someone walks out of your life, should they be able to walk back in?

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I'm totally losing my mind right now. For those who read my last post, Ryan & I didn't click like I thought we were going to, but it's okay :). But now... Out of nowhere, and ex boyfriend popped up on Facebook, and we were talking. We have a child together and really haven't talked since my son was born. (He has always been in our son's life though). Well, we were IMing each other and he said "So when are you going to come see me?" And I laughed it off saying I couldn't leave then state til Nov. And He replied with "Well, maybe I should come down there." I'm a little bit confused at this point. Then he tells me that he thinks about the old days all the time and misses me really bad and if he came down here we should try and work it out. Now, we broke up last year, while I was still pregnant with our son. And all I wanted was an apology and such and he just took it as a sign and left. And I haven't had really any contact with him besides our son. So, really what I'm asking is, if a relationship was perfect, and it ended because of hormones, should I really give him a second chance? Should I go out on a limb and try it again. Or should I just let it be and keep going the path I am. I have been missing him lately and I think it's a sign. BUt I need some other opinions. Please help me out :)