The Bend "Balloon Man" will take to the skies again this Saturday, relaxing on his lawn-chair packed with enough balloons to help him float for miles.  He hopes to float for at least 13.5 hours and 250 miles to get in the Guinness Book of World Records.  So- why does Kent Couch bring a BB gun with him?   " I use the Daisy Red Rider; use it to shoot the balloons down.  Don't want to go up to 25,000, up and down up and down.”  But couch won't be alone on the 6-by-7-foot balloon-mobile; he's taking along Capt. Fareed Lafta, of Dubai, an Iraqi pilot who set a Guinness Book World Record for skydiving over Mount Everest.  The public is invited to watch the men prepare for takeoff Saturday at Couch's Stop & Go Station at the corner of  Highway 20 and Northeast 27th Street in Bend.  Takeoff is scheduled for 10 a.m.