clean installing mountain lion while keeping snow leopard?

Hello, I have a question...

I newly buy an SSD and at the same time I am thinking to upgrading to Mountain Lion... My operating system is snow leopard now.

I am thinking to download Mountain Lion and make a bootable flash disk. Then cleanly install it to the SSD. I dont want to touch my Macintosh HD... I am not a good technician... is it possible? I am doing this becuase if I dont like performance of mountaion lion, I will re-install the snow leopard to SSD... is it possible? Or After I boot from SSD, will I able to boot from again Macintosh HD (Snow leopard)??