Boy, I wouldn't. Bottling in growlers is pretty dangerous as it is, as they aren't designed to hold pressure for carbonating. More than a few pictures have been posted on this forum of growlers blowing up. They are meant to only store already carbonated beers, short term.
I'd use soda bottles for bottling if I didn't have enough beer bottles or caps.
Broken Leg Brewery
Giving beer a leg to stand on since 2006