If you look at the 'Law' book, I think you will find that it is illegal to glass in your balcony in Spain. I know it sounds daft, especially as every 2nd place has glassed in balconies, but there you are. Having taken that info as fact, then the town hall cannot give you permission to do the glassing in, even if they do turn a blind eye to it.
Our community voted at an earlier AGM to allow glassing in ( as long as the design was similar ) and our administrator said that would be sufficient ( although now, after learning more about the Spanish system, I would question whether we really could grant this permission at AGM as it is against Spainish law )
Anyway a good third of the apartments have glassed in balconies and I know for a fact that the town hall has not been approached about any of them.