One can assume Simba learned of what direction his homeland was in from Timon and Pumbaa over those 4-5 or so years he spent with them. Going by Timon's wording about how Simba was "THE king," it implies he and probably Pumbaa have some familiarity with the Pride Lands and its monarchy(and if we're to count 1 1/2, then obviously they'd most definitely know). During some random talks, they may have discussed about the place and where it lied at some point.
What's interesting is that Simba was supposedly going to have a few small adventures throughout the film, both during his time growing up alongside those two, and when he heads back home. For the latter, he would have gone through treacherous areas and bypassing the spot where the Be Prepared sequence took place before finally making it back home, apparently. It gets a mention here in a developer's Let's Play video for the game a few months back:
https://youtu.be/kILeyo1iv0A?t=42m34s