I'm starting to find Google+ communities that I really want to join now - but, as predicted, it's getting a bit cluttered in there. Google have just helped improve the situation a little though.
As well as being able to adjust the volume on your circles , you can now choose whether or not to have your posts in communities appear on your profile page. Just click through to https://www.google.com/settings/plus or the cog > settings and scroll down to 'Show your Google+ communities posts on the Posts tab of your Google+ profile.' Remember that posts you make in communities won't appear in the newsfeeds of those who have circled you in any case, unless they belong to the same community. (More info on communities here.)
A good move I think - nice to be able to choose whether you have the chat within your hobby 'Knit Lego Mini Figs' community appearing in the same broadcast space as your blog posts and social media strategy musings. As one commenter has already pointed out, it would be good to have the granularity to decide to do this community by community, but hey, it's a start.