Yes, robotically. We should invest in more and more research on mars using remotely operated, autonomous and semi-autonomous robotic explorers. We should send vehicles that can land on the surface and return with samples. We should remotely build and operate small habitats that could sustain human life and see how well that can be managed. Then with all of that, if we discover something that a human mission should warrant and we have already created a sustainable habitat, send people.
Mars is not a life boat. While we are capable of wrecking the suitability of Earth for sustaining its soon to be 9 billion people, we aren't in danger of making the earth a less hospitable place than Mars for human habitation. Fixing our world is far more easier, cheaper and sustainable than living off of it. But Mars as a scientific and research outpost may be worth while. After a 100 years the human footprint in Antarctica is still quite small and is just scientists and support people. Antarctica is an easy to get to paradise compared to Mars.