Skype Number on IPhone for Roaming?

Will be heading to mexico for a bit. I have an unlocked iphone 4s. I will definitely get a sim card and data plan in mexico and i read telcel is the company that i should sign up for when i get there. But of course thats for data there and probably minutes i could only use locally in mexico.
However i heard one could make phone calls with skype as long as you have data. Can someone tell me how this works? First off, i would need a skype number right? And i have to pay for this and its a 1 time fee or yearly fee?
Do i need to create this number before i leave the usa?
At the moment i dont have a carrier with my phone as it doesnt have any service. So when i get to mexico, i would use the hotel wifi in the meanntime until i go and get data. Then when i do get a plan, im sure it wont have minutes to the usa so i figure best option is to use the data or use my computer to call back to the usa right? I believe its a few cents a minute only?

OK, lots of things to address in this post.

If you are on WiFi
[ul]
[li]Calls to other Skype users around the world are free.[/li][li]Calls to landline/mobile will cost Skype credits. Cost will depend on where you’re calling and which package you buy. For example, you can pay by the minute, or purchase a package of 60 min./month. Unit cost of pay-by-the-minute is usually the most expensive. Inversely, the more minutes you buy in a package, the cheaper the unit cost. Calls to the USA the last time I checked was something like 2.5 cents/min. without a package.[/ul][/li]
If you on a data plan (ie. 3G/LTE)
[ul]
[li]Calls to other Skype users are free. You only pay for data. If you’re only doing voice calls and not video, you’ll be using approximately 1.5MB per minute.[/li][li]Calls to landline/mobile will cost Skype credits, same as above, plus data usage.[/li][/ul]

You do not need a Skype number. That is only if you want someone to give you a call on Skype and but they are not a Skype user. They would use a regular phone to call your Skype number which you would receive through Skype.

You can also use Google Hangouts instead of Skype and calls to the US/Canada are mostly all free.

Even Skype has a $2.99/mo plan for unlimited calling to the US and Canada.

Thank you for this information. The thing is the persons that i will be in contact with won’t be contacting me using skype. Thus if im using wifi and could use skype, and they are using skype, yes i know we could chat or video call for free. This is the they using a landline or mobile phone.
About the skype number, so if i don’t have a skype number and i call them using the credits, what phone number would show up on their phone then?
Yes most of the time it will be me calling them but if i wanted a skype number, how does that work? I read you could sign up for monthly plan or 3 month play or 1 year plan. I only want 3 month max and then go from there. I mean, i wouldn’t mind using it 1 month just to test it out. But would i have to get this skype number in the usa first before i go outside the usa?

Isn’t there a restriction on google hangouts such as you can only use it in usa or canada and to usa or canada only? I would be planning to be in mexico. Does it work there?
Yes i heard about the skype plan you mention. Seems much better than the pay as you go as theres a connection fee each time per call. But you can use it in mexico? I read something where data plans there blocks skype though not sure 100 percent.

No idea.

If the person wants to contact you from a phone, you will need to get a Skype number. If you are on WiFi when the call comes in, there will be no charge to you. If you are on cellular, you only pay for data.

You can register your mobile number to show up as caller ID. If you have a Skype number, you can use that or your mobile phone number. In theory, any number can be used as long as it can receive SMS because that’s where they send the confirmation code in order to register your number.

You can get a Skype number wherever and whenever you want to. I’m in Japan, but I could buy a US number right now if I wanted to. The good thing about this is, if I have someone from the USA who needs to call me, the US Skype number would be treated as a local call so international rates would not apply.

The Skype number plans are different depending on region. I believe you can buy them in 1, 3, and 12 month plans in the USA. Make sure you cancel your plan early if you don’t plan to use the number in the future because they are renewed automatically. You can cancel the day after your purchase and you will still be able to use it for the term of your plan.