Yes, of course it should - and it will, if a person has honestly committed his or her life to Jesus Christ. In fact, if there isn't any change in a person's life after they profess faith in Christ, their faith is not real. The Bible says, "Faith without deeds is dead" (James 2:26).
Why is this true? The reason is because when we come to Christ, God Himself comes to live within us by His Holy Spirit. You can't be the same once God lives within you - and you won't be. You'll begin to see sin for what it really is: rebellion against God. You'll also want to please God, because you'll realize that He put you here for a purpose - and that purpose is to live for Him.
This doesn't mean, however, that Christians are perfect, or that they'll never struggle with sin - not at all. Satan will do everything he can to pull us down - and although God now lives within us, so does our old sinful nature. The Bible says, "The sinful nature desires what is contrary to the Spirit. ... They are in conflict with each other" (Galatians 5:17).
My prayer is that you won't allow the inconsistency of a few people who claim to be Christians keep you from Christ. Look at Him, for He alone is perfect, and He alone can give you the forgiveness and new life you need. Open your heart and life to Him today.