Going off the top of my head, you could set up a list of coordinates, in an array for example, which say where the player 'lands' when she leaves the house. So when you go to the island screen, you'll have a 'On start of layout' event which checks where the player came from (I'd store that in a global variable, so when you leave a house, set a variable to the number of the house which was left), then you can check your array for the coordinates to place the player at.
Or, you could have special tiles (like a sort of 'doorstep' tile) which are placed outside each house, which look the same (or you could make them look differently, like a different doormat for each) but have a certain value connected to them. Then when you leave the house, again set the global variable ('WhichHouseLeft' or something) to the house number, then you pick the tile which has the value, e.g DoorMatTiles > Number = WhichHouseLeft ... then place the player on that tile.
I'm just winging it here but that might give you some ideas.
Either way, you're probably going to need to use a global variable. Don't be afraid of them, they're really useful and easy to use and don't HAVE to be messy if you use them sparingly.
Cute game by the way, stick with it :)