The 'legal' ratio in California is set at 12 - 1 for children who are three years of age. What you want to do is to find out what the qualifications are of the teachers you are seeing in the classroom. There should be at least one who is "fully qualified". Then there can be one who is considered an aide. Depending on the education of the aide, that can add from three to twelve more children to the classroom.
I would talk with the administration of the daycare and request that the two teachers with whom you are familiar and comfortable be scheduled so that one of them opens in the morning and the other closes. That way you'll always (except possibly in the case of an emergency or teacher vacation time) have someone with whom you are familiar and can depend on the information you get being accurate. Then begin to make an effort to become more acquainted with each teacher you encounter in the classroom. There should be at least some consistency with which they are putting other teachers with the children. If it continues to be altogether too much change and too often, you again should talk with the administrators. Daycares sometimes, in looking for the bottom line of profit, do forget to keep proper consistency in staffing the rooms. I say this from years of experience working in daycare centers. The only way it's going to change is for you to speak up.