I was at Costco yesterday, and I noticed they were selling some Mountain Bikes. I don't remember the name, but I know they had a Shimano gear set, and didn't weigh that much, but they were not super-light either. They had front and rear suspension's, and cost around $150 I think. I think I would trust buying a cheap bike from Costco more than I would from Walmart/Kmart/Target... Any suggestions?