Should Christians rely on horoscopes and astrology?

No, Christians should not rely on these things.  God did create the sun, moon, and stars for signs, seasons, days, and years for man to use (Genesis 1:4).  Also, some constellations are mentioned in the Bible (Job 9:9).  However, the act of using these things to try to predict life events and relying on them to guide a person’s decisions should not be done.  This system was created at the Tower of Babel, the beginning of paganism.  The Bible states that we are not to follow witchcraft, sorcery, and observation of times (2 Chronicles 33:6).  We are not to use these things within our lives because they are of the Devil.  We are to trust in God and put our faith in Him in all things, allowing Him to direct our lives at all times (Proverbs 3:5-6; Matthew 6:25-34).