In my opinion traveling to mars is at the present time to dangerous and unnecessary to attempt until at least we have better, more advanced technology that takes away some of the massive risks we would face if we were to undertake such a mission at the moment. Although traveling to mars is feasible it is also inadvisable and would put the crew of the vessel that attempted it at a great many risks that shouldn't need to be taken, and for the little that we would likely learn from this mission would be unnecessary and very expensive.
The longest astronauts have stayed in space for any period of time in transit is at present a matter of months, and severe muscle deterioration as well as psychological strain from the relative isolation and cabin fever have been recorded. These effects would be much more severe should we attempt to send people to mars as the minimum time that such a voyage would take is at least a year and a half. It is likely however that setbacks and mechanical difficulties could well make this figure a lot bigger as well. This being the case it could well mean that any people sent could be physically and psychologically damaged irreparably, and the level of muscle degradation due to weightlessness could reach such levels on the journey as to make them unable to carry out their duties when or even before they arrived.
Once on the planets surface the astronauts would also probably need some way of producing their own food if they were staying for any length of time, as not enough dry packed food could be taken on board the shuttle to last several people for a period of time approaching two years. Also if there were any kind of mechanical or electronic problems whilst on the planets surface the astronauts would be on their own, as help would be far too far away to be able to aid them in time, and even communications from earth would be at a several hour delay due to the atmospheric pressure of mars and the distances involved, so any repairs etc would need to be made solely by the astronauts, without much help from the controllers back on earth. As well as this there are frequent and violent storms on the surface of mars, that could well damage equipment or cause a break down in communications altogether, leaving the astronauts stranded until they starved to death.
Because of all the extra risks and the periods of time involved the undertaking of a mission such as this would be by far the biggest that mankind has even undertaken. The shuttle would have to be larger then normal to encompass all the extra fuel needed for both the way there and the return journey as well as all the extra equipment and food needed to survive on the planets surface. These things would also mean that there would need to be more astronauts than normal, meaning the shuttle would have to be bigger still to house them all once they had landed.
All this extra equipment and the sheer size of the mission would also mean that it would by far be the most expensive single undertaking in mankind's history, which a lot of people would say could have been spent better on problems the country has rather then being in reality wasted to see if something is possible without getting that much in return. As well as this if anything happened to the astronauts whilst on the mission, or even if their health was seriously decremented upon their return, then the reaction form the public could well endanger the funding for the entire space program altogether.
These risks being the case i think that with current technology and capabilities it is completely unnecessary to send a manned mission to mars at the moment. I think perhaps when technology has improved by a lot so that the time taken to reach mars would be at least halved, and when there are more safety measures in place that would ensure the safety of the astronauts better then this question could be readdressed, but for now i don't think we are technologically ready to undertake a mission such as this.