As Mars stands now, probably centuries. Maybe millennia, or even indefinitely. Mars lacks most of the weathering mechanisms Earth has: there's no oxygen so nothing oxides (rusts), there's no water, and while dust storms are fast and kick up a lot of tiny particles, the low atmospheric pressure means that there's simply not a lot of force behind those winds. (It's said on Earth that it's not that the air is moving, it's what the air is moving. On Mars, "what" doesn't amount to much.) Meteorites on the Martian surface can persist for millions of years and still be recognizable.
So, assuming that you're after the bulk structure of a rover and not its electronics (the plutonium core of Curiosity's RTG will be long dead, let alone previous rovers' solar panels), it can last quite a long time indeed. By the time they've landed, the rovers have faced the biggest mechanical stresses they're ever likely to. Maybe the biggest threat is that, over the course of millennia, they end up on the downwind side of a rock and become buried in dust.
But, your Mars is terraformed. What effect will that have?
Surprisingly, for all the intricate detail about what goes into Mars landers, the basic construction of the chassis doesn't come up much. However, it seems reasonable to assume that none of materials that would be on the short list to send to Mars are all that volatile. Plastics don't do very well in low-pressure environments, and there's no reason to send nice oxidizable iron and steel when there's plenty of aerospace-grade aluminum and titanium to go around.
Assuming the rover body is rustproof, it shouldn't be unduly affected by oxygen in the atmosphere, or by increased pressure. (Rovers undergo engineering tests on Earth, so they can handle Earthlike pressure, and gravity for that matter.) If it can avoid being physically weathered (read: hit by a rock) it should be good for a prolonged period, possibly into the centuries.
Incidentally, I would use Curiosity rather than Spirit or Opportunity, partially because it's about five times the size, but mostly because it has a signed plaque and, according to this article, was also signed by the student who named it. Whether these would survive the elements is less certain. (If they were laser-engraved, the signatures should last a fair amount of time if not worn down by dust.) However, I think it's neat to think about.
(Little Bobby should not tamper with the aforementioned RTG. As long as it's in its housing, he's safe, but if he opens it up he may end up inhaling plutonium dust which is, I should stress, not good for you.)
As for whether it would be well-known, probably in general terms but maybe not by sight. At least in my experience with public school history, "how we got here" is a major topic, and rovers as a whole probably played a vital part in establishing a Mars colony. Individual rovers, however, might be less important - especially since we don't know what missions may be launched in the future. There were a number of lunar rovers that were important and impressive in their time but have already been overshadowed by the dramatic accomplishments of our current crop of Mars rovers; the future might hold more of the same that would obscure this particular wreck's place in history - at least for awhile.
As an example: you probably remember, as I do, that Columbus's flagship was the Santa Maria. You might remember that it was a design the English call a "carrack", larger than his other exploration ships. But could you pick it out in a lineup of sailing vessels?