buongiorno,
I was also a 28 year old Italian engineer when I applied to St. Gallen MBA.
I believe it is a great program and I do recommend it to my friends.
I agree with you that you will not be fluent in German in one year but I can reassure you that German is not a problem at all in Switzerland for MBA level jobs, unless you want to work as a local consultant or in private wealth management for Swiss. Basically none of the students speak German and the large majority finds good jobs here in Switzerland.
St. Gallen as a school has a very good reputation all over the world, however the MBA is still young and not well known (even in Swizterland).
I hope this helps you make your choice!
saluti,
massimo