Angela Park (65), Yu Ping Lin (65), and Silvia Cavalleri (68) shared the lead at 9-under 137 on the hilly Tres Marias course.
Sarah Lee matched the LPGA Tour record for relation to par for nine holes, shooting an 8-under 28 on the front nine -- her final nine -- en route to a 66. She was a stroke behind the leader at 8 under.
Ochoa, who took the top spot in the rankings from Annika Sorenstam on Monday, had four birdies and five bogeys. She struggled with her putting and also left herself in difficult positions with some poor approach shots.
'I lost my rhythm. It wasn't the wind. I'm a player who can play well with a lot of wind. It was just a bad day,' said Ochoa, who was followed by hundreds of fans, giving warm cheers and clapping even as dropped strokes with bogeys.
'But I'm still in the tournaments. Maybe tomorrow there will be less wind and I will be able to play more aggressively.'
Ochoa won last year on the Jack Nicklaus-designed course that sits 6,300 feet above sea level -- and is 175 miles from her native Guadalajara.
Park birdied her final five holes.
'I'm optimistic after such a great round today. Obviously there is still two more days, and a lot of holes to play,' the South Korean player said. 'Nothing is really going to change tomorrow. I'm just to keep on doing what I'm doing and hopefully get some good results on Saturday and Sunday.'
Cavalleri, from Italy, had a bogey-free round.
'I'm feeling really, really well and like the course,' Cavalleri said. 'Some of the holes remind me of the course in the Italian Open that I have played for quite a few years. I like it.'
Teresa Lu (68), Julieta Granada (68) and Pat Hurst (69) were 7 under, and first-round leader Stacy Prammanasudh (73) was 6 under along with Na On Min (72).
Two players had aces Friday.
Diana D'Alessio holed a 4-iron shot from 186 yards on the 13th.
'I really didn't hit the best shot of my life,' D'Alessio said. 'I kind of pulled the 4-iron a little bit and hit into the bank and I turned my back and the crowd up at the green was like, `It went in!'' she said. 'I laughed so hard. I was like there is just no way. That was just a thrill.'
D'Alessio's also had an eagle in a 67 that left her tied with Ochoa at 4 under.
Ji Yeon Lee had her hole-in-one on No. 6, hitting a 9-iron from 139 yards. She finished with a 75 and was 3 over overall.