R.P.
I have a two y/o born the same yr/ month as yours. Maybe it is something about Septemeber of '06. *smile* My daughter use to get up at 5am like clockwork too. I attributed this to my husband's alarm clock ringing at that time and my early rising to get "Me Time" in. We couldn't explain the weekend early rising. I workout early in the morning, read and do homework, so I need the children to remain in bed. I will share with you what works for me.
I limit her nap to no longer than 1 1/2 hrs during the day including weekends. I also changed her nap time from 11am to 1pm. Since you cannot change the day care's nap time you can do this on the weekend. My daughter is potty trained, so she will get up and go to the restroom on her own. What works for us is to have her books next to her bed in a small bin.
Instead of coming to our room or yelling out, she will sit in her bed and read. My daugthers have wall lights in their room that illuminate as like a soft pink colored light. We use it as a night light for them. Her bedtime is between 8-8:30pm. It use to be earlier, but I had to slowly work her to the later hour due to her early rising.
Changing what time she goes to bed in the evening, her nap time and limiting the amount of time that she sleeps has helped. She still may wake early on occasion, but knows to stay in her bed and read or play until we come get her (or her siblings get her). Sometimes she even grabs a toy out of their toy bin and gets back into her bed to play quietly. Hope this helps!