A long, long time ago -- at least in terms of today's schizophrenic markets -- I urged investors to take a long, hard look at shares of America Movil (NYSE:AMX), Latin America's largest wireless player. I was intrigued by the company's rapid subscriber growth, its success in entering into new markets, the low cellular penetration rate in its target markets, and its reasonable valuation.

Since that bygone time (late last September, for you history buffs), shares of America Movil have risen some 27%, handily beating the 11% return posted by the AMEX Mexico Index over the same period, and thumping the mere 7% gain managed by the NYSE Composite Index.

Of course, I may have simply been lucky on a short-term call. The real question: What lies in this stock's future? Given the political uncertainty in the Mexican presidential election, and the great investing herd's recent aversion to emerging markets in general, is it a good time to lock in the profits?

In my Foolish opinion, the answer would be a resounding "no." In fact, I believe that shares of America Movil are even more attractive now than back in September, and that investors shouldn't even consider hanging up on this stock.

All four legs of my original investment thesis remain intact. Subscriber growth continues to grow by leaps and bounds, the company continues to successfully enter new markets, Latin American wireless penetration rates remain low, and best of all, earnings expansion has made America Movil's valuation even more attractive than ever.

Subscriber growth
After adding a net 7.3 million subscribers in the first fiscal quarter ended March 31, 2006, America Movil boasted more than 100 million total wireless subscribers. That's a 7.8% increase sequentially, and more than 51% ahead of its 66 million cellular customers in the first quarter of 2005.

While America Movil is projecting a marked deceleration in subscriber growth in 2006 as it succumbs to the law of large numbers, the company's goal of adding a net 25 million subscribers still represents a roughly 27% increase in its customer base for the year. Since it has historically been conservative in its projections, I suspect that this number will likely be substantially higher, especially since America Movil continues its relentless march into new markets.

New markets
At the time of my article last September, America Movil had wireless operations in eleven different markets. Today, it operates in fourteen, with the three new operations -- Chile, Paraguay, and Peru -- tallying 4.4 million subscribers as of the end of the first quarter. That's an average 17% sequentially, and more than 75% ahead of last year's period (if you use an apples-to-apples comparison).

This ability to successfully target, integrate, and grow acquisitions should continue to benefit shareholders. The company is set to expand into two new markets through its recent agreement to purchase Verizon's (NYSE:VZ) operations in the Dominican Republic and Puerto Rico. The deal will add an estimated 2.3 million wireless subscribers, and 1.7 million landlines, to America Movil's portfolio.

Low penetration rates
Like behemoth China Mobile (NYSE:CHL), America Movil operates in an area where cellular penetration rates lag the global norm. At present, penetration rates in Latin America are roughly 43%, significantly below the 90%-plus rate of Western Europe and the 70%-plus rate in the U.S. That leaves ample room for organic growth.

Despite the advance in shares over the past few months, America Movil's multiple has actually compressed as earnings skyrocketed. The stock now trades at approximately 18 times fiscal 2006 earnings estimates of $1.92 per share. That's an 18% discount to the 22 times earnings at which I originally recommended it, and in line with its long-term projected growth rate. In contrast, other wireless plays such as Vodafone (NYSE:VOD) and China Mobile trade at substantial premiums to downright anemic projected growth rates.

In short, America Movil remains my favorite pick in the wireless space. I'd urge potential investors in this industry to take a closer look.

Vodafone is a Motley Fool Inside Value selection. Discover additional value opportunities with a free 30-day guest pass to Philip Durell's premium newsletter service.

Fool contributor Will Frankenhoff is enjoying his time writing for The Fool more than playing golf, reading The Financial Times, or taking a nap. He welcomes your feedback. He does not own shares in any of the companies mentioned above. The Fool has a disclosure policy.