The positions specified are for the 1st day of the given month at about 9PM. This should apply to the whole month for all of the planets except perhaps Venus, which moves very quickly.
Month Venus Mars Jupiter Saturn Uranus Neptune Pluto Jan Cap E Leo Psc Vir Psc Aqr Sgr Feb Aqr E Vir Ari Vir Psc Aqr Sgr Mar Psc E Leo Ari Vir Psc Aqr Sgr Apr Tau E Leo Ari Vir Psc Aqr Sgr May Tau E Leo Ari Vir Psc Aqr Sgr Jun Tau O Leo Tau Vir Cet Aqr Sgr Jul Tau M Vir Tau Vir Psc Aqr Sgr Aug Tau M Vir Tau Vir Cet Aqr Sgr Sep Gem M Vir Tau Vir Cet Aqr Sgr Oct Leo M Lib Tau Vir Psc Aqr Sgr Nov Vir M Oph Tau Vir Psc Aqr Sgr Dec Lib M Sgr Tau Vir Psc Aqr Sgr
Venus is only visible just before the Sun rises or just after it sets. The letter after Venus' constellation refers to when it is visible.
When a planet is on the opposite side of the sky from the Sun from our point of view, it is called opposition. When a planet is at opposition, it is usually at its closest point to the Earth. Since Venus and Mercury are inner planets, they can never be at opposition from our point of view. Mars typically goes into opposition every 25 to 26 months.
Mars goes into opposition on Mar 3, 2012