There are physical limits to efficiency. In different technologies were are different distances away, but there are always limits that we cannot exceed. We can get creative about not needing to get close to the limit, but the limits are always there stopping us.
I doubt it. Maybe mars and venus, but even there getting self sustaining is going to be hard. There is no reason to suspect that we will ever be able to get anywhere else with less than a generation ship, and no reason to believe we can make one them them that will work long enough...
