Linux is almost certainly available in your country. In any case, it is free to download, or $2-$4 for a mail order CD. It's best to buy it with a book, though. At a bookstore it's $20-$40 for a CD with a manual.
I use Linux exclusively. Windows is expensive, slow, unstable, intentionally not reverse compatible, insecure, etc.
I don't have any opinion on Mac, except that they are expensive and usually impossible to upgrade.
Linux is free, fast, secure, and fun! I use computers because I like them; I don't need hundreds and hundreds of megs of Microsoft safety padding around my machine.