The optimist in me says, "yes". We've proven to be pretty decent at figuring things out, after all. From crossing oceans to going deep under the ocean surface to sending people to the Moon, not to mention surviving for many many years in prehistory when we didn't have so many advantages over mastodons and saber-toothed tigers as we do today.
We've also proven that we're not half bad at introducing flora and fauna to non-native areas, sometimes without even trying to do so. Thus, if the hypothetical planet is sufficiently Earth-like, we could likely figure out how to grow at least a subset of our native plants there as well. We don't need all of the soil to be good for growing tomatoes, for example. We just need some of our crops to grow well.
I also wouldn't be surprised if some of the local flora and fauna proved to be edible and non-toxic. Identifying which was edible and non-toxic might be a problem at first. But assuming we've identified a sufficiently similar planet, there may well be sources of sugars and fats and proteins. We've proven remarkably adaptable to highly processed foods, why not some alien plants as well?
Of course a lot of that hinges on just how "Earth-like" the planet is...
NukeAJS raises a very interesting point about travel times and colonist priorities, however. One of the things I loved about the film Sunshine is how things start going haywire as soon as the ship is outside of the radio communication zone with Earth and they have to start making their own decisions. Do they stick with the mission plan as originally stated? You'll have to watch the film to find out, but you can probably guess... if it really does take decades or longer for a fully active crew to reach the new planet, there's a major risk that they'll decide something else looks like a shinier, or just more convenient, destination. We could probably even dig up examples from the history of seafaring to illustrate that, and not just the early 1492-era ones where new landmasses were discovered, but likely later on when the captain or (mutinous) crew decides the original plan wasn't so great after all and why don't we go to this nice nearby tropical island instead?
The pessimistic answer would be, are we going to make it long enough as a species to get to that other planet before we nuke our technology back to the stone age? Which is all the more reason to start sending people to the Moon and Mars to hang out for a decade or two and learn more about living in space, sooner rather than later, if you ask me. That would also likely spur R&D into spacefaring survival, which surely hasn't been as much of a priority as it was in the 1960s, considering that it's been nearly 50 years since a human set foot on the Moon.