Narci, I'd love to put him on a schedule but when he scratches the balcony door to go out I've no idea if he wants to fool around or pee/poop, and I can't risk saying "no" because then he'll go inside.
You'll have to 'teach' him that outside is for poop and pee.
Like misstray said, you need to watch for subtle signs.
If you take him out, be firm that it's meant for potty. Don't play with him and set a time limit. Example, if he doesn't do business within 5-10 minutes..back inside.
Remember to praise him a lot when he does do his business. We use to give Oreo a treat when he poop or peed.
Inside, you can do the same. When he poops or pees at the place you want him to...praise and reward him (High reward treat, might want to stick with a certain reward that's he LOVES as the only treat he'll get if he pees or poos in the right spot.) but you need to do it just as he finishes. No point in praising and treating when he's done it some time ago.
Once he know that he gets lots of praise and treats for doing something he will learn fast.
If he doesn't poop or pee in the right place, clean it up and ignore.
Most of all, you have to have a lot of patience. Training a dog isn't a one time affair. They learn by repeating over and over.
Of course this is only my opinion as this method has worked for me.