We have been Virgin Mobile customers for years. Always have good service in WDW.
Right now, they have a phone for $19.99, that includes $20 of air time...so it is like getting the phone for free. The air time is good for 90 days, at which time you have to top up another $20 if you want to keep your service active. (or you can do $10 every 45 days).
http://www.virginmobileusa.com/cell-phones/kyocera-s2100-phone.jsp
I have the pay as you go plan and average around $6 / month.