I'm sure it varies by region, but in Bohemia (present-day Czech Republic, historically the northernmost reaches of the Habsburg Empire) the answer is a measly one or two.

Budweisers, though – which is to say the people who lived in Budweis, as it's known in German, or Budějovice in Czech – were known for their unusually high rate of bilingualism. An estimate made in 1865 by the Czech-language newspaper Budivoj guessed that 60% of Budweisers were bilingual; a disappointing number for one who imagines a continent of roaming polyglots, but that 60% estimate is subject to due scrutiny.

The "Revolutions" of 1848 had given rise to nationalist movements across the continent (which many historians consider a catalyst that led Europe to collapse upon itself in World War I) and Budweis/Budějovice soon succumbed to nationalist tensions that challenged and tested any who refused to consider themselves Czech or German, but instead simply a part of the "Budweiser" nation.

By 1862, tensions had spilled over in an unlikely venue for Ultranationalist sentiment: singing choirs. Follow the link below and read page 4 for the full story, but even ridicule and sarcasm took on a bilingual form. After a rousing rendition of "What Is the German's Fatherland?" sung not once, but twice, the German Ultras stood up and cheered "Bravo"... in German, as well as with tongue-in-cheek cries of Vyborně in Czech.

https://books.google.com/books?id=Q9vFaJt98hIC&lpg=PP1&pg=PA4#v=onepage&q&f=false

If you believe the estimate given by a Czech-language newspaper in the middle of a national "renaissance" then it's only 60%. For a more in-depth examination of Central Europe, though, the above book is a great start.

Budweisers into Czechs and Germans: A Local History of Bohemian Politics, 1848-1948 Jeremy King, 2005 (Princeton University Press)