So Bush wants to send men to the Moon and Mars just like his father did. The estimated cost given to his Dad was 500 billion and the topic was quietly dropped. I wonder what's changed? The cost would still be enormous and for what? Bragging rights?
I should admit I've been indocrinated in enough sci-fi and Star Trek to quite like the idea of space exploration. Let's terraform Mars. Sure. It's a long term goal we can work on over the next few hundred years.
So the program needs a good vision and slow, steady progress on a series of worthwhile goals with consistent funding. I think the President can provide the vision but he shouldn't be setting the timeline. Personally, I don't see the point of going back to the Moon; a space station makes more sense. And it's seems pointless to send people to Mars when robotics would be much more risk averse and cost effective. But I'm no rocket scientist.
For an interesting story about colonising Mars, I can highly recommend reading Red Mars by Kim Stanley Robinson (Nebula Award 1993). His approach is scientifically accurate but the future history is even more entertaining. It's part of a trilogy but Red Mars was the first book and best book in the series. It's followed by Green Mars and Blue Mars but I found the story really started dragging out too much in the remaining books.