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 Lib M Sgr Psc Vir Psc Cap Sgr Feb Sgr M Cap Psc Vir Psc Aqr Sgr Mar Cap M Aqr Cet Vir Psc Aqr Sgr Apr Aqr M Psc Psc Vir Psc Aqr Sgr May Psc M Psc Psc Vir Psc Aqr Sgr Jun Ari M Ari Psc Vir Psc Aqr Sgr Jul Tau M Tau Ari Vir Psc Aqr Sgr Aug Cnc O Tau Ari Vir Psc Aqr Sgr Sep Leo O Gem Ari Vir Psc Aqr Sgr Oct Vir E Cnc Ari Vir Psc Aqr Sgr Nov Lib E Leo Ari Vir Psc Aqr Sgr Dec Sgr E Leo Ari 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 does not go into opposition in 2011