If the Qs are bad at the weekend, try the ballymount dump(sorry, civic amenity centre) instead, no more then 5-6 minutes drive if youre on the M50 anyway. take the ballymount exit, go into the industrial estate and follow the signs.
Ive never been longer then 2 minutes in a queue there (when theres been one) and Ive been going on saturdays regularly for the last 3 years.