In the third day of a seemingly endless bachelor party in Cabo San Lucas last year, Hal Walker, 33, woke up with a set of classic symptoms. His head ached. Loud noises made him wince. Bright lights hurt his eyes. Mr. Walker's flight home from Mexico to Colorado, where he is now a co-owner of the Island Grill in Fort Collins, left at 8 a.m., and it was all he could do to get to the airport. "If you can find a remedy for hangovers, that would be great," he said, voicing a sentiment familiar to anyone who has imbibed...