In the United States, endometriosis affects 6-7% of the female population.
More Info: Endometriosis affects an average of 176 million women worldwide, more than 5 million in North America. Statistics for endometriosis are often best guess estimates as the condition often goes unreported as well as the fact that it is often misdiagnosed. 
Basic Endometriosis Statistics
Many women experience the symptoms of endometriosis for nearly ten years before being diagnosed with the condition making twenty-seven the average age of an endometriosis diagnosis. 
Women at the highest risk for endometriosis are Caucasian, have a relative with the condition, have an abnormal uterus, or have had their first child after the age of thirty. 
How Common Is Infertility with Endometriosis?
Of the identified causes of female infertility, endometriosis is third behind the failure to ovulate and poorly functioning fallopian tubes. It is estimated that endometriosis is the cause of infertility in 10% of the cases that have had the cause identified.  Interestingly, though not always identified as the cause, endometriosis can be found in 24-50% of women who experience infertility. 
Not all women who have endometriosis will have trouble conceiving. Infertility issues are dependent upon the severity of the condition and the location of the endometrial tissue implants. For example, a woman may have trouble conceiving if the additional tissue is blocking the normal path of the egg from the ovaries through the fallopian tubes. It is estimated that 30-40% of women with endometriosis have trouble getting pregnant. Fortunately, many cases of infertility caused by endometriosis can be corrected with minor surgery. 
How Successful Is Surgery?
In the case where surgery for endometriosis preserves fertility, as opposed to hysterectomy, 60-80% of the cases successfully improve pain short term. Within two years 40-80% of women experience recurring pain. In the case of full hysterectomy, removing both ovaries, 90% of women experience complete relief. 
 Endometriosis Foundation of America
Endometriosis Facts and Statistics
 The University of Chicago Medicine
What Causes Female Infertility?
 American Society for Reproductive Medicine
Facts about Endometriosis