The road to Ensenada is paved with serious sweat and goofy get-ups. At 10 a.m. Saturday, 10,000 bicyclists in the Rosarito Ensenada 50 Mile Fun Bicycle Ride will push south from Rosarito Beach on the bucolic free road that hugs the Baja coast, one most motorists skip in favor of the faster toll road. They may crank alongside a cowboy wearing a 6-gallon bike helmet, a milkmaid in a billowing skirt with blond braids, a super-sized SpongeBob SquarePants (best costume of 2003) or racers shooting to break the course record of two hours, 12 minutes. Around the halfway point, the mob shifts inland and hits the legendary El Tigre -- a backbreaking 7.5 %-grade climb of 800 feet over two miles. (Remember, this is fun.) At this point, walking is no embarrassment. "For many people, it's the most radical thing they've ever done on a bike," says ride director Gary Foster, noting that two guys died after facing El Tigre last year. Survivors spin back out to the ocean and a slam-dunk downhill into Ensenada, where they receive a hand-painted 14-color medal (the first time in the ride's 25 years that every finisher gets one) and a finish-line cerveza. Well, maybe more than one at the massive post-ride fiesta with bands, food and, yes, more beer. Most riders finish in three or four hours, though some struggle in after six. Warning: This twice-a-year party on wheels may become addictive. Wilford Melton, 56, of Monterey Park has logged more than 40 rides since 1982. Go to www.rosaritoensenada.com or call (858) 483-8777.