It's kind of hard to tell you exactly what to say. There are too many variables. What if you, at the moment, don't understand her (or their) ansewrs> What if they ask you something that you don't fully understand> Or what if they give you some adress or directions you can't follow nor understand at the time>

Also... I don't fully understand what you exactly need. Do you want to know how to adress the subject with Mexican scorts> Or you know what to say and you just need to know how to say it in spanish>

Whatever the case, it would be better for you to call a girl who fully speaks english or be, at the moment you call, with someone who can translate both ways (no pun intended )

Regards
Malapropina