Yes, it is safe for a single female to travel in Ensenada, most people in Ensenada love and treat well foreigners. Most everyone would like you to be their friend and will assist you in many ways.
I travel to Ensenada very often and have not had any problems, even my wife has been vacationing over there alone. As a matter of fact, I have owned a vacation home over there for six years and I have felt the safety that prevails in that town. I have also seen lots of tourist visiting all the time, and not only North Americans, but also Mexicans from other states and cities, who claim that they love Ensenada because of their beauty people and safety. The city is patrolled by the local police and the Mexican Army and no one messes around with the army in Mexico. Ensenada may be one of the safest cities in Baja for many reason. one of them is that the Ensenada Port receives varios Cruise Ships every week with hundreds of tourist from LA and other cities in Mexico. The authorities make sure that the town is "tourist safe" because their economy partially depends on foreigners visiting or living in Ensenada. There are hundreds of American and Canadian citizens who are retired and living "the good life" in Ensenada. I have talked to some of them because I will retire over there and I hear from them that they are living happy that they all feel safe .