The hard part about sending a person to another planet is keeping him or her alive. People require, at the very least, a certain amount of food, water, and oxygen to survive. It costs a lot of money to launch payloads into space, about $10,000 per pound. How much "stuff" do think it would take to get some to another planet? How much would it cost? A trip to another planet would probably take several months or years depending on which planet.

There is also an issue on how a person traveling in space for a long time would be effected medically and psychologically. Muscles and bones might atrophy with the lack of gravity. People might have a hard time being in a very enclosed space for months on end. Humans weren't really designed with space travel in mind.

NASA is very much working on the issue of manned space travel. I'm sure they are planning to send people to Mars some time in the next century. There is still quite a bit of work to do before that can happen though.

Well, we probably could send someone to Jupiter or even to Mars, but it would cost a lot of money.The cost of space travel is one reason that we haven't sent anyone to the moon in over 20 years. We could send people back to the moon, but most people think that the money is simply better spent elsewhere. Likewise, we probably could send some people to Mars, but a lot of people think that that trip would cost nearly one trillion dollars. A trip to Jupiter would cost many times more than a trip to Mars, and so we won't be seeing either of these events for quite some time. If we are ever going to send some people to Mars or to Jupiter, scientists and engineers are going to have to find ways to reduce the costs of space travel. First and foremost, we are going to have to find a way to reduce the cost of lifting materials from the Earth's surface into earth orbit. Remember that the astronauts will need to carry enough fuel to get them to their planet, enough fuel to get back, and enough food, water, and oxygen to sustain them during their trip. The longer the trip, the more stuff that needs to be lifted into space resulting in higher costs. A trip to Jupiter would take many years, requiring a lot of fuel, food, water, and oxygen. One way to reduce the amount of stuff that must be brought along is to shorten the trip by developing faster spacecraft. There was an interesting article in Scientific American a few months back that talks about research into faster spacecraft. I highly recommend this article if you are interested in this subject.
My last point is that while we might see a manned trip to Mars in our lifetimes, I don't think that we will see a manned trip to Jupiter. In addition to the costs of going all the way to Jupiter, since Jupiter is a gaseous planet, there is no solid surface for the astronauts to visit. We can probably learn as much about Jupiter with unmanned probes as we could with a manned mission.