When you are a fan of the blues songs you cannot help but learn guitar and its goes the same way the other way round. That is, if you are a guitar player you cannot keep yourself from the blues. However, it is by far easier to become a blues guitar player when you are already trained in singing the songs because you have a good understanding of how the blues work. But it is a hard road when you are trying to get your guitar to play blues for you because the basic thing that is required before you can excel in the blues is a good understanding of how the scale of the song works and the run on lines and everything else.
But since the basic is learning the music itself properly, you will do well to listen to some blues songs first. You will find tons of blues songs on the Internet.