English level is middling.
Under 35 locals.... Odds are good they will speak at least a little. Maybe 75% I'd guess?
The older you get the more things shift onto German though.
Also consider that Lausanne is nearly half foreigners; a fairly large group of English speaking expats for a city of the size and a large number of people from Latin countries who generally don't speak English (though some do).
You can get by with English just fine though don't be surprised when you run into shop workers who can't speak it at all.