There are several ways to ask if one speaks Spanish. If you are asking a friend or someone younger, you would say "¿Hablas español?" If you are asking an elder, family member, teacher, etc....
"Do you speak Spanish" would come in two forms, depending on to whom you are speaking. For a formal tone, one would use "¿Habla usted español?". Informally, it would be "¿Hablas español?"
"No hablo espanol"- I don't speak Spanish"No puedo habalr espanol" - I am not able to speak Spanish.(The n in espanol has a tilde [a wavy line] over it)