Yes, cycling is really good for you; especially since you will be out in the fresh air!!!! I do a lot of cycling in the summer as we live in the country and have a great cycle track near us.
It is good for the good old legs and depending on how fast you go it helps to speed up your metabolism.
It depends what type of bike you want...I would personally go and sit on one. I always do because you might like the look of a bike and then it is uncomfortable for one thing or another.
I have one of the modular city bikes, but got special tyres so that I could go on the tracke. It is a very heavy bike but I feel safe on it. Some people prefer the other ones with the really thin wheels, and the strange handlebars, but I dont. So, I would suggest you go to a bike shop and try them all out, and then take a note of the make/model and then you might find one cheaper online.
Good luck though...it is such a lovely way to excercise and enjoyable too!!
I love cycling & will cycle to work when I can, we also cycle at the weekend as a hobby. At the moment I'm trying to get into mountain bike riding. We bought mountain bikes recently from Halfords & the guy was very helpful. He asked loads of questions & made recomendations on the best bike for us.