Ochoa was coming off an opening 76, her highest score in nearly a year.
Im happy with my round. It was a good day, said Ochoa, who had four birdies and two bogeys Saturday on the hilly Bosque Real course. I wasnt able to get a lot of birdies, but I still really want to tomorrow. Im not putting the desire to win the tournament out of my head. You never know what will happen.
Oh, a 19-year-old from South Korea in her second season on the LPGA Tour, had five birdies in a bogey-free 67 to top the leaderboard at 9-under 135.
I like this course. Mexicos elevation is high, so when you hit the ball it goes really far, said Oh, whose only top-10 finish on the LPGA Tour was a sixth at the Safeway Classic last year. I just feel good. Tomorrow I just think I should enjoy it. Either I win, or come in second, I dont know.
Taiwans Yani Tseng, a 19-year-old rookie, was 7 under after a 69. Swedens Eva Dahllof (70) was 5 under, and first-round leader Jill McGill (73) and South Korean rookie Na-Yeon Choi (66) were 6 under. Chois 66 was the best of the day.
Ochoa, a budding national hero more popular in Mexico than the sport that she plays, packed in the crowds at Bosque Real as hundreds of fans snaked down the fairways, erupting in pounding applause and cheers of Lo-re, muy bien!
She is a really dignified, admirable person. Her strength, her wins and her humility have raised Mexico to new heights across the world, said Marcela Livas, 70, who traveled 400 miles from Monterrey to watch Ochoa on Saturday.
The crowds cheered for every golfer'but little girls dashed from hole to hole in baseball caps and bows following Ochoa, while neighbors stole out into their backyards, straining over bushes alongside their uniformed maids to catch a glimpse as the two-time Rolex player of the year passed by.
Its exciting, said Emiliano Camarena, 13, an aspiring golfer who sat cross-legged with 10-year-old brother Alonso in the thick ryegrass as Ochoa worked her way down the 10th hole. Shes the first Mexican to be No. 1 in the world, and that makes you feel like you can do anything.
Ochoa, who opened her season two weeks ago in Singapore with an 11-stroke victory in the HSBC Womens Champions, has struggled to seal the deal in Mexico, with one victory in six previous LPGA Tour starts in the country.
I always want more, the 18-time tour winner said. Id love to be in first place right now, but we have to think about accepting our errors and our bad moments, too. Yesterday wasnt good, today was better, and we hope that tomorrow will be even better still.
We hope to put one a really good show.
U.S. rookie Hwanhee Lee had a hole-in-one, the first on the LPGA Tour this year, on the 189-yard seventh hole. Lee, who used a 5-iron, finished with a 78 to miss the cut.