I think you can only have 1 blog per account? I don't use the blog function very often on myspace, so i'm not certain... however, you can chose to make which entries private or public, or allow only certain people to view.
Yeah..either you should make two different accounts, one for each group of people you want to see, or make the blogs private so only certain members of your friends list can view it (you can specify it after you create the blog).