Anyway back to Ankara...
Yes the drive is straight forward and all major roads so you should have no problems. However Ankara itself is a nightmare to drive in if you dont know your way around. I've Turkish friends that refuse to drive in Ankara.
Have you considered the overnight bus option?
It is very cheap and the coaches are modern and confortable with stewards serving tea/coffee etc throught the trip. They leave Fethiye every evening around 9:30 - 10:00 and arrive in Ankara around 7:00 the next morning with a couple of 20 minute stops on the way.
Also the Taxi's in Ankara are cheap and plentiful so getting about should be no problem