Of course, technically the answer is yes. And there is no strict policy since Golos is not on live yet. I suppose it will be permitted by community to have some content in English by appropriate tagging like here, in steem, russian posts tagged in "ru" category.
RE: #1 Golos Weekly Report Oct. 09, 2016: Network Launch, Crowdsale Delay, and How Golos Will Differ from Steem