B.P.
Hi K.,
I can feel your pain, I am single mom too, working full time, plus going to school full time. Unfortunetely Plano does not have a lot of cheap daycare. Have you ever tried Child care services?
http://www.twc.state.tx.us/svcs/childcare/ccinfo.html
They helped me for a long time, I think you do have to meet some salary guidlines, but it is worth a try.
My son goes to daycare in McKinney, there are some good daycares. The one that he goes to is only 110/week.
I live in Plano though but I work in McKinney, so its not that way far out for me, actually I can spend more time with him this way in the morning and in the afternoon!
Good luck!
B.