I would suggest doing some quick tests to check what setup works best - for example by region-rendering for a defined amount of time. Generally you do not want any objects “outside” of the portal, but in this case two options are possible:
-place portal close to the glass, like in normal windows
-place the portal close to the balcony opening, as it it was a window
I think the 2nd option should work best.
Yup, Tanakov, you should definitely show your works more often.
Also, you should put more thumbnails in the 1st post to draw more attention. There are many awesome pictures hidden in the Google Photos link you posted.