First, best of luck with a speedy recovery in time for volleyball try outs! As a former volleyball player myself I know how important those try outs are! You can focus on seated upper body and core workout options which will help you be at your best for setting, hitting and serving drills. This link will take you to a variety of seated workout videos on the site to help you stay on track with your weight loss goals as well as getting you ready for try outs! teens.sparkpeople.com/resource/videos-cate
As far as your weight loss goal -- slow and steady weight loss while growing, developing and being at your best for volleyball are all important goals. To accomplish this you will need to be eating at least 1800 calories to fuel your body and encourage it to use reserve fat stores for energy. It may mean you need to take a little longer to reach your weight loss goal but it will also mean that you did it in a healthy way for long term success.