Since you do not return to the balloon (it leaves), the question may refer to the Poptropica blimp. To leave the island, fly back to the Mews mansion on the helicopter, then walk left past the house to the gate, and out to Mansion Row.
The only hot air balloon is the one that you cut loose on Cryptids Island. There is the Poptropica Blimp, which will take you to Main Street on any of the islands, if you climb the rope and click "travel."
Go to the store and buy a sports drink for the thirsty gardener. You can use his garden shears at the the far left of the island, to cut loose a hot air balloon.
The hot air balloon is tied up to the lighthouse at the left side of Cliff Park (left of Main Street). Get the $5 bill from the tree by the mansions and buy a sports drink for the gardener, and use his shears to cut loose the balloon.
go farthest to the left of the island and climb up the lighthouse you'll see a guy in a hot air balloon. talk to him then go to items get the shears and cut the string.
Get the $5 bill from the tree at the right of mansion row, and buy a sports drink for the thirsty gardener. He will loan you his shears.
There is no yarn in a tree that you can get. There is a $5 bill in a tree, and there is some nylon rope at Cliff Park -- cut loose the hot air balloon with the garden shears.
you have to go to the conducter in the front and talk to him
There is a $5 bill in the tree on Mansion Row. Buy a sports drink for the thirsty gardener, and use his shears to cut loose the hot air balloon at Cliff Park.
The hot air balloon is in the tower.
The shears are used to cut loose a hot air balloon at Cliff Park (gives you some rope), and at the end of the quest to cut loose a cage holding Bigfoot.
Give the hang glider girl a shove on the rocks by the lighthouse, and use the garden shears to cut loose the hot air balloon. This gives you some nylon rope and you can borrow the KiteSurfer from the kite store, and come back to try it out at the lighthouse.
Get the $5 from the tree at the right on Mansion Row, buy a sports drink, and give it to the thirsty gardener. Go far left to Cliff Park and cut loose the hot air balloon.