If someone posts a URL to a G+ post, you can most certainly view it without being logged-in. (Try it: go to your G+ stream, and then for a post, select "Link to this post" on the drop-down menu, then past that into a Incognito window --- you'll be able to view the post.) You can also view a user's G+ profile, and view all of their public posts, without being logged in.
Yes, you won't be able to create a stream and follow a set of users without creating a G+ account --- but without a G+ account, there's no place to actually store the set of users / G+ pages / G+ communities that you're interested in....
It's strange that I hear that from a lot of G+ users. I personally find that when I try to visit even links from HN pointing toward G+ posts, I am forced (well, prompted) to log in. For that reason alone I've never actually seen a post on google plus.
Yes, you won't be able to create a stream and follow a set of users without creating a G+ account --- but without a G+ account, there's no place to actually store the set of users / G+ pages / G+ communities that you're interested in....