I've been using skype with my son in S. Korea for almost two years now.
We talk on skype with laptops though, no phone or ipads, etc. I know the application is available for those modes too, just can't offer any advice.
From computer to computer, it's free for video, txt to txt, or just voice. You can even conference call with a three way for free (only voice though, no 3-way videos).
If you want to call from your computer to a land line there is a charge. Skype credits are real cheap. When we want to video chat with our son and he isn't online, we call from the laptop to his landline and tell him to skype with us. Takes about 10 seconds and I can't even tell you how cheap it is. We originally bought a whopping $10 in skype credits two years ago, have used it 1/2 dozen maybe 8 or 9 times like I explained, and we STILL have $7.50 left in skype credits.
I would definitely play with it a bit while you're home, just to learn the nuances of it and then you can figure out how the whole international thing works.
Skype is the best invention since white bread. :redface:
Have fun........on skype and in Mexico
Russ