You may get as good a deal from your cell phone carrier as you'd get from a VOIP providerCell phone deals for calls within Mexico are tricky. Calls TO Mexico are loudly advertised. They won't tell you have bad a deal they have FROM Mexico or WITHIN the country.
I bought a TelCelUSA plan with unlimited calling to and from Mexico for not much money.They eliminated that plan without telling me and customer service was very aggravating. Then I found Simple Mobile. Unlimited calling to and from Mexico and Internet. We'll see how long it lasts. It is without a contract. You need an unlocked phone and a sim card to get something like this.
For residences, VOIP phones have the advantage of being pretty consistently good. They are better than Skype, but so many people use Skype and are so sold on it that it is like a religion to them. Try both and make up your own mind.
Skype is low-cost alternative, but the quality is still not up to VOIP standards. I use Skype computer to computer service when I travel and found it tolerable, but not something I would use to conduct business. The video chat is a nice feature, but only about 50% of the time did I get a consistent-enough signal for it to work well. But, if you are traveling and calling home to your honey, free is pretty nice. If you use their paid service, it seems to work pretty well. If you call friends and family who have Skype, it works fine - IF you have a good, fast Internet connection. Otherwise it is frustrating.
Until you get all set up with a home phone, it would be wise to get a cell phone for your travels. If you get an unlocked phone (from these folks below or anywhere else), you can get a SIM card that will let you use the TelCel network (via AT$T) for less. Or you can just rent a phone if you are afraid of commitment.
Most businesses in Mexico have VOIP phones with a U.S. and a Canadian phone number for their clients to call.
Imagine, though, having a US phone number while living in Mexico so you can call home or conduct business without paying long-distance charges!
In general VOIP calls (in Mexico or the U.S. or Canada) are as good as land line calls, However, occasionally you will have a slight lag, but in most cases it is hardly noticeable anymore. That used to be the bane of VOIP phone calls. I also found that getting a good-quality phone helped tremendously. A 5.8 or 6.0 megahertz phone (is recommended to avoid conflicting with your wireless broadband connection.