Hi Tarnya bummer on the broken leg! But don't let that stoo you from losing weight. I am counting calories and eating 1800 cal a day and also I am on the Alli diet and it is working so far.
I started Dec1 at a gym and when I started I couldn't do 15 minutes on an elliptical machine, 2 months later I can run at full speed for 60 minutes so your body can adapt very quickly.
You can work your upper body until your leg heals. Movement is movement and it will burn calories maybe not as much as running or walking but every little bit help!
Limiting your calorie intake is where you'll burn calories. And I have learned that even though I am eating smaller portions (meals under 400 calories) I eat 4 times a day with two snacks and I am never hungry.
I wish you luck you can do it!