I play the clarinet but i reallt wnat to play sx and i heard it was realley easy to swithch between the two is that true.

Would it be a good idea to learn sax too.

Ya it is pretty easy with some practice. Just make sure that while you are learning the sax to continue to play the clarinet a lot because the sax embochure is loser in the middle then on the clarinet so if you don`t practice on the clarinet as much while you are learning it will screw up your clarinet embochure and then it will take a while for you to get your lips tight enough again. Go for it, the sax is way cool if you are planning on playing jazz.

I took up the tenor saxophone a year after learning clarinet...both are simular but they are different in tone quality, how you put the mouthpiece in your mouth, etc.

For Bb clarinet...I suggest Bb tenor sax unless you want to learn how to transpose....also they sound simular.

It`s always a good idea to learn how to play several instruments, it gives you more opportunities later on. So I would say, go for it!