Yes! Skipping is good for you and also alot of fun! :) So I woiuld definatly do it! Even if you do 15 minutes of skipping each day you will be healtheir! :)
skipping can really get your heart rate up, so yeah it is good cardio exercise. As far as it being the only exercise you get- not so good.
If you're just starting to exercise, try to have about 30 minutes a day for 5-6 time a week of your heart rate being elevated. Skipping can definitely do this (and if you are like me and can't actually jump high enough, skip with an imaginary rope). But remember you also need to work your skeletal muscles as well -so look into something that will help strengthen the rest of your muscles in addition to skipping. This might be aerobics or weight training, whatever takes your fancy. After a while you might want to add on another 30 minutes or so of exercise a day. Just try not to exercise more than 2 hours or 6 days a week as it could put a lot of stress on your body.