the elliptical too, but not to worry - there are lots of other kinds of cardio you can do. Really, any exercise is cardiovascular if it raises
your heart rate for a defined period of time. I wouldn't classify lunges as cardio - unless you want to do them continuously for 30 minutes! - but the bike and treadmill are both excellent. Then there's also outdoor running or walking, swimming, and other kinds of cardio machines, like stairsteppers, stepmills, and crosstrainers (I don't know if you have access to a gym).
For maximum fat loss when you're doing cardio, do intervals of moderate intensity alternating with high intensity.
Good luck - you'll do fine!