Whoah, you got the lens early. o.o! How did you get the lens? Even I have trouble getting the lens. x X. I mean don't you need a lot of Relics to get past the archaeologists in the excavation first?
Anyway, you go to the very northwest to get the dream whistle. From the swamp, pretty much hug the left side of the map upwards for a bit until you get to the lost hills. I think the maze path there is south north east north. Then it's pretty much linear to the Dreameater city.
Once you get the Whistle, you can go into Pulchera village and start using the whistle next to sleeping people.
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EDIT: Aww, I even did the hall of statues miniboss to unlock the cliff entrance. D: Man, that sucks. I'll have to go fix that. Okay, I'll upload a new version in a few.
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'tis updated!Even included ... er ... quite a few shortcuts to various places in the Deku Jungle. I included a permanent secret trigger just outside the cliff-side entrance, so you don't have to go fuXx1ng around the hall of statues to get that thing open again.
Oh. Fun fact: The L4 sword now does 9 damage instead of 8. Say goodbye to those annoying blue wizzrobes and like likes. >:-p
But just to be clear, in that save file, I really did defeat the hall of statues miniboss to open the cliff face entrance. I guess it didn't take or something. I never even touched it before.
Pre-2.5 non-local secret triggering is really weird. It's based on level numbers and boss rooms and secrets being triggered. When you have so many level numbers to keep track of, stuff gets all wonky. I'm glad we're in 2.5 here, so the end-solution will be simpler.
EDIT again: Okay, I think that the cliff-side entrance is actually opened when you defeat either the first or second of the boss-repeats in the Deku Tree. I didn't defeat the third one yet, and when I went to the entrance of the Deku Tree on F-1, it opened.

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I just beat the game. ^-^
woo
So yeah, it's beatable now, from Deku Tree onward.
(Download the above file again, as of 10:33 PM EST, 5/3/12.)
There was a nasty layer problem on the last repeat-bosses, where layer 2 was fully solid so you couldn't walk. That sucked. D: