Some of that depends on which carrier you use. Before Verizon took over Alltell, I loved the latter's plan for free Mexico roaming, but Verizon doesn't have one.
They told me that they did when I discussed the vague description on their site in 2009, but they were wrong and that could have been an expensive mistake to argue if I had used the Unlimited After 9pm minutes extensively like I did on Alltell before evacuating in advance of hurricane Dean - with the company calling the decision.

Calling Continental Air's local and Mexico toll free numbers was impossible that week so I was calling their Houston number, along with calls home.
I guess a lot of cell phone users today may not remember the old Home areas of the area cell phone carriers maybe? With my first cell plan, I could use my phone without roaming charges in northwest Texas only. :shocked2: Calling across the street while in Dallas or Florida was quite expensive. Today, Verizon phones aren't supposed to work in Mexico unless you call to ask for that option, then will cost you $1/minute locally
I think,* more to call long distance, much more to call the US, and then there the extra charges for texting and/or data which can be significant.
* These things change so rapidly tho, it's wise to talk with your carrier, even if it's the same as mine - and hope they know what they're saying. I'm not supposed to receive texts when in Mexico but often do on my old phone; I never try texting from there.
ATT&T may have more & better options internationally, the others...?
Nowadays, I carry a headset and use Sykpe - on my laptop or a public computer. I forgot my headset once, and it's rude to use one's laptop speakers in a public place - but the airline earphones I'd kept on the flight in worked ok after removing an adapter

along with the built-in mic on my laptop.
Now, there is no roaming issue with Skype as they look at calls as if they were placed from your home: 2.3¢/min to 49 states, 6¢/min to Alaska, 2.3¢ to 10.5¢/min to non-mobile numbers in Mexico, 33.6¢/min to mobile numbers! :shocked2: I use the hotel room phone to call my dive shop, but to call off of the island - I don't know. Where do you want to call? Most hotels have room phones I think, some may not, hotel policies may vary, so - where are you staying?