There's really no such thing as Cheap practice around here unless you can get to a sunday special at one of the northern VA Bowl Americas.  Edsal Rd has a Sunday special that's pretty cheap and in the summertime on Tuesdays from 9-11:30 is a 6 dollar all you can bowl which is a great deal.  There's not many big leagues in the summertime that I know of except Big Bucks Mixed Doubles in Bowl America Edsal Rd Tuesdays at 6.  Just visit as many centers as you can.  In this area there's about 12-15 to choose from, and pick up alot of flyers.
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-DJ Marshall
"Repetition beats luck everytime"