Ciganda had a bogey-free opening round at Club de Golf Mexico.
''I really like this course,'' Ciganda said. ''I really like it because is really similar to my home course in Spain.''
The former Arizona State player won last month in South Korea for her first LPGA Tour title.
''I was home last week and I played four tournaments in Asia, so it was really nice to be home with my family,'' Ciganda said. ''I didn't practice at all. It was just resting and having fun, going out for dinner with friends. And I feel very mentally refreshed, because in Asia I was a little bit tired at the end. It is important how to manage all the tournaments and all the weeks you want to play.''
Smith played the back nine in 5-under 31 after bogeying Nos. 8 and 9 to make the turn at even par. The Australian is winless on the LPGA Tour.
''It makes a difference when you see it,'' Smith said about playing alongside Ciganda. ''I love playing with her, she is so nice and we always have fun, so it absolutely makes a difference.''
''I was feeling really good,'' Fassi said. ''I worked really hard on preparing for this tournament and on the first tee when they said my name I was nervous, I am not going to lie, but after I hit the fairway on the first tee, I was like, 'OK you got it, just enjoy your round.' And that's what I did. ... I was really solid off the tee. I gave myself a lot of opportunities to be a little bit more aggressive on my second shots.''
Michelle Wie opened with a 70. The 2009 winner in Guadalajara, she's also playing on a sponsor invite after failing to qualify for the 30-player event.
Canada's Brooke Henderson, the highest-ranked player in the field at No. 7 in the world, had a double bogey in a 74. No. 14 Anna Nordqvist also struggled, making a double bogey in a 75.