PHILADELPHIA Tired of life with her children and their father, Carmen Ramirez decided last summer that it was her time to have some fun. So, police said, the 27-year-old began to spend more time with a boyfriend and left her five young children - including her severely disabled 3-year-old daughter, Nathalyz Rivera - with their father in a West Oak Lane home so filthy and bug-ridden that police wore Hazmat suits when they went inside.