Do People Every Really Change?

I've been having this dilemma lately.  There are people in my life that I've told to go away and then let them back in time and time again.   I keep hoping that maybe they have changed like they say they have.  Yet I am almost always disappointed to see that nothing has changed and I am again the sucker.  If there is a pattern in your life where people are constantly telling you that they need to be away from you what do you think the common denominator is?  I know that I have made some changes to myself over the years because I saw a pattern that I wasn't to happy to keep on living.  Now here I am stuck into another pattern. Am I a fool for thinking and believing that people can actually change the person that they are?  I have friends who think I'm stupid for being friends with my ex boyfriend after all that he and I had been through.  But you know if I can't forgive the people who truly hurt me then what is the point of forgiveness?  For all you church goers, aren't we always taught that Jesus forgives us all for everything we do?  All the religious people of the world are aspiring to be like Jesus (or whichever deity they pray to) so why can't forgiveness be the first step?  I will always give someone the benefit of the doubt.  I will allow them back into my life slowly and see how that goes.  As of now the ex that I befriended again has only shown me the side of him that I fell for in the first place.  Maybe because I'm in a different forgiving stage in my life.  But point of the matter is that I feel he may have actually changed the way he and I interact.  No more fighting, no more arguing and no more hurting each others feelings on purpose.  Am I fool to think that he's different?  Or is this all a facade because he needs something?  I would hate to go around thinking that people are only treating me nice because they want something from me.  To me that sounds like a sad way to view the world and to a sad way to view others.