Can I legally change my daughters last name there 4 and 2yrs old there father did not sign the birth certificate and hasn't been in either of there lives for 2 yrs!!

No. If you go to court to request a name change, the court will require that you get the father's permission. If the father is not listed on the birth certificate, then the court will require you identify him and get his permission.

If you do not know where he is or how to contact him, you will be required to show that you made a good faith effort to get his permission.