Just outside of the secret passage is a man selling some simple healing items. Buy some if you need to, but keep in mind that there is a Magic Butterfly spawn point to the north, not too far away. You can use that to heal up for free.
Make your Way North to Saturn Valley
Collect items along the way north. Eventually you will come across a cave entrance on the right. Go inside. Go through the short cave, picking up a gift box along the way, to reach Saturn Valley.
Saturn Valley is a cool little town. It is populated by Mr. Saturn, all of whom look exactly alike: pink creatures with two short legs, no arms, a big nose, whiskers, two black eyes, and a single strand of hair with a red bow tied around it. They are all named Mr. Saturn. Also, it looks really cool when they talk. So talk to them!
Visit the Saturn Valley Hospital if you have a mini-ghost. Dr. Saturn will get rid of it for you.
Talk to Mr. Saturn to get the Password
A Mr. Saturn in a cave will tell you the secret of getting into the Grapefruit Falls base. The secret is, when the guard asks you for the password, to stand still and wait for three minutes. You have to talk to this particular Mr. Saturn in order for this to work, though!