I did an away rotation first, in July, having never done ortho before. It was great for a couple of reasons:
1. you are likely to be the only student there, especially if there's no associated medical school. This makes you memorable and will give you flexibility on which cases you scrub.
2. Everyone will be out of sorts with the new residency turnover, making your mistakes, such as they may be, much less noticeable. Keep in mind though, this may give you an unfair negative impression of the program.
Study hard beforehand and you will be remembered at your away location. When you get home, you will be compared to the other students from your school (who did their sub i in july or are doing their first 4th year ortho rotation) and, having just done an ortho rotation, you will be way ahead.
Bottom line, if you can swing it, this will put you ahead of the game.