Suitable

That's the key word really - it has to be suitable. Not all 3G technologies are the same. It's a term used by mobile (cell) phone companies all around the world for very varied services with incompatible hardware.

The 3G service from Telcel is, to describe it technically, a UMTS HSDPA service, operating on the 850MHz band. So that's the technology any hardware you get has to be compatible with.

Major carriers like Verizon and Sprint in the US use a very different "3G" technology, so won't work here. 3G outside of North America and Australasia is on the 2100 MHz band, so again that's not compatible. What you need is something that does UMTS/HSDPA on 850MHz (looks like the iPhone 3G and 3GS do, for example).

There is one further thing - the phone or modem has to be "unlocked" - capable of running on any carrier. If you've brought it on a contract from (for example) AT&T, it is probably locked to their network. You need to pay them (or somebody else) to unlock it before you can use it on another network.

Local Dongles

Given the above, the simplest solution to connect a computer is to buy a 3G dongle (modem) direct from a Telcel dealer here in San Felipe. There are some deals around for about $120 including the first month of service (using prepaid, not a contract). These prices will vary. That'll be for a USB stick-like dongle that plugs into a USB port on your Windows, Mac or Linux computer. The dongle takes a Telcel Amigo sim card inside it (that's the account), picks up the 3G signal from the phone tower, and looks like a dial-up modem to your computer (but is faster!). It should have installation instructions and local help.

If you know what you're doing, you can also pick up suitable modems on ebay and so on for around $50-$80, but be sure they are unlocked and have the 850Mhz. Some of the model numbers sold locally are also available in different band versions for other parts of the world, so triple-check it supports the right band. If in doubt, buy locally.

One disadvantage of a dongle is you need a Telcel account just for that. You can take the sim card out of the dongle and put it in a GSM phone to make a call if you have to, but really it's best to work on the basis of one sim per device, so it's effectively a data-only sim.

Phones

You don't need a computer to access the internet. Many modern "smartphones" do the job, especially if you don't mind squinting at teeny little screens and have tiny pointy fingers to press the keyboard or touchscreen. Some examples are the Nokia E51, the iPhone 3G/3GS, and basically anything that supports UMTS on 850MHz. Again you can buy phones like this locally, and if buying elsewhere make sure it is unlocked and has the right band.

Although web browsing on these phones is rarely enjoyable, it is at least mostly possible, email works OK, and there are internet phone applications that run on some of them so you can use the data connection to make and receive much cheaper phone calls. For somebody who just wants to contact others and be contactable by email and voice, they are a great deal simpler than messing around with a computer.

Phone to computer

If you're an infrequent user of the internet, it's also possible to use a suitable UMTS phone (as described above) to connect to the Telcel data service, then it relays that connection to your computer through a cable or other connection.

To be honest this can be technically fiddly to setup and isn't really recommended. It ties up your phone while you're online and has another link to go wrong. The connection between the phone and the computer is a special data cable (can be costly for older phones) or a bluetooth radio connection, if both your phone and computer have that.

Phone connected to computer by bluetooth is what I used for initial testing, but I soon replaced that with a modem (dongle), so that I can use my phone for other things, like making calls!

Sharing the connection

Once you have a faster connection you'll maybe want to share it with multiple computers in your house (I have). This is a whole separate subject, which I'll describe later. But in summary you could: use "internet sharing" or similar on your computers (so the one connected to the internet has to be switched on all the time) or do something similar with a home server computer that routes out to wi-fi to send the signal around.

And there are "mobile routers" than accept a dongle (or have one built in) and provide a wi-fi signal directly (again with these, be careful, as just because it is 3G does not mean it works here).

Success

When you've connected successfully, let us all know what you've done, how well it works and anything special you need to do to set it up. You can add a comment below and it'll appear (after I've checked it for spam) below this post, for others to learn from.

I don't use a wide variety of technology (and what I do use tends to be non-mainstream) so comments from others locally who have different models and operating systems (Windows etc) will be very helpful to us all. The same applies to any message here - the comments section is for you to add to the discussion, and point out my mistakes. Thanks!