Cycling does build leg strength, especially in your quads, but since it's not weight bearing, it's not as effective as, say, running. You will notice changes in your muscle tone and definition as you continue to ride, but if muscle toning is your primary goal, I would also recommend doing some weight/ resistance training for both your upper and lower body.
Well, you are very right... it's not a weight bearing exercise.
From my own experience though, I use to go to the gym and do squats/lunges/running/etc. etc. (This was before I got into cycling.)
My legs looked good, but they weren't "WOW".
Ever since I started cycling... I always get compliments on my legs when I wear shorts. Now days, my legs are "WOW". So, even though it's not weight bearing, it sure did help me out a lot.
Jill, go to a spin class. Those bikes in the class are 100 times better than a stationary bike. Otherwise, you can follow the instructor on what to do.
For me, though... I never follow the instructor. What they do in a spin class, I would never do on my real bike. For example: They will turn the tension all the way up and mash on the pedals. In a real-life biking scenario, I would downshift and make it easier to pedal. The key in cycling is having high cadence. It's not about muscling through the pedal strokes. So, I basically go in there and spin (literally) for 1 hour.
Good luck, and get a real bike as soon as you feel comfortable with the idea. It's so much fun. My time flies when I'm out on my bike where as the minutes slowly tick by in a spin class.
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather, to skid in broadside thoroughly used-up, totally worn out, and loudly proclaiming: WOW WHAT A RIDE!!!!"