Learn something about Mexican culture. Learn some Spanish. I think one has to have a positive regard for Mexican culture in order to establish a successful relationship with a Mexican woman. And this can only come with being somewhat informed about Mexico. Once there, I think a two-week stay would be a minimum.
Communications are a bit slower in Mexico.
Actually, they were indispensable. You also need time to do your homework and preparation. This means going through the profile sheets and filtering down the prospects until you get a manageable list. There are a lot of women in the Mexican Ladies book. You will have to take the time to survey the field.