I have decided to configure my WordPress blog so that users have to be registered and logged in in order to post (by using the admin setting by going to Settings, Discussion, and clicking on "Users must be registered and logged in to comment").
How can I have both "Log In" and "Register" offered on my WordPress blog?
Under settings > General, make sure "Anyone can register" is checked.
If I allow membership to anyone on my WordPress blog, does this mean that anyone can create a blog?
If by "blog" you mean a post/article? This would still depend on the "role" the user is assigned under. There is a drop down right below the checkbox I mentioned above that sets teh default role of newly registered users: More info...