You guys talk about a lot of things like they're magic. Having a garden, for example. Having a garden requires either soil that has been well-prepared by many years of soil evolution, or a metric ass-load of chemical fertilizers. Chemical fertilizers require a pretty hefty industrial infrastructure. You planning on building fertilizer plants on Mars? Just getting a portion of Mars to the level that you could do sustainable farming would require decades of supply lines. Hydroponics is no answer, because you still need plenty of chemical fertilizers--even more than dirt farming.
And how about replacement parts? Lubricants? Coolants? You planning on building chemical manufacture plants on Mars for all of this? What resources does Mars have that you could use to synthesize lubricants? What process would you use? How much money would developing that infrastructure cost?
Now, yes, Mars has evidence of plenty of the kind of volcanic activity required to be able to find the various ores and minerals you would need. But the facilities to process these are enormous. We have them on Earth, built up over centuries of the industrial revolution. But to start from scratch on Mars will require enormous expenditure, and frankly there isn't an economy on the planet right now that could support such an expenditure. Worse, it would be a long-term massive expenditure, and what happens to the project, and the people trapped on Mars, when it becomes obvious that it is unsustainable?
Building a Mars colony isn't like building a Starcraft base. You can't just magically turn vespene gas into 30 weight oil to lube your engine. The processing infrastructure that even shit like that requires is enormous and complex. Plus, the titanic influx of essentially free and easy fossil fuel energy has instilled within us the mistaken assumption that growth is unlimited, and that the stars are within our reach. The truth is, the free ride is just about over and finding sustainable resource sources simply to keep our own planet going is going to become orders of magnitude more complex. Trying to keep our planet going AND build a new one from scratch on the same horribly limited resource budget is just not going to work.
on the other hand, you make it sound like it's going to have to support a city's worth of people from the start.
the resources to support a small colony(4-20 people for the first decade or so) is quite small, and is completely within reason to do so. mars has similar ore resources to earth, the entire infrastructure for power, food, air, and water well be uniquely tailored to mars, it's highly likly that a mars colony well be using some very experimental tools/ideas to create oxygen, water and food. it's really not unreasonable that we couldn't get a small colony going that is capable of sustaining itself. nothing has to be built to industrial scale for quite some time.
the very first priority is going to be to get the colony to self-sustaining capability, no one is going into this without that understanding(or so i'd hope anyways).
remember that necessity is the mother of invention, who knows what radical new technology's may evolve to solve these problems.