First, it apparently is necessary to bring to the attention of many the simple fact that the Spanish-speaking market for this game resides mainly outside of the borders of the United States; learning English there is as much an imperative as learning Spanish is to American nationals, but not an ounce more. Keep this in mind before you self-righteously order people to learn your own language: It apparently escapes you that we're talking about a game that has been translated for you, just because of the fact that the American population is unlikely to suddenly learn Japanese.
The global Spanish-speaking market is way larger in population and potential than the already very saturated North American market is. Rates of economic growth in both Portuguese and Spanish speaking countries rank higher even than those of Asian countries, and by the year 2015 (that's barely a few months longer than a year away) Brazil, Mexico, Colombia, Argentina, and possibly Chile are likely to have positioned themselves as larger economies than most countries in Europe.
And that's only 5 countries out of 21 (!) that speak Spanish within this hemisphere. Don't count Brazil's huge potential, because they speak Portuguese there, and still, the other 4 will have a combined market impact, due to, GDP, population numbers, upward mobility, lack of penetration and increase of acquisitive power, larger than France or the UK have today. If you add Spain (which alone boasts 50 million people and which, for the geographically challenged out there, is a large and normally prosperous economy in Europe, even if--like most of that continent right now--it's currently undergoing a hard recession) the obviousness of the market advantage for a Spanish localization just hits the ceiling.
Think of it this way, there's no language in the world today, not even Chinese, that appears as a better option for this game, especially from the perspective of the American player base: Most of these countries are within one of the Contiguous 48's four time zones, and the few that aren't are just one hour off. Think of the increased market potential and consequent sustainability that a single translation would afford your dear game, to say nothing of the multiplied opportunities that come with a synchronous player base.
Another factoid to round up this claim: The combined population of just the 10 largest Latin American cities is already more than one third of the TOTAL population of the thousands of cities, towns, villages, and rural municipalities contained in the whole of North America, and yes that includes Canada. And all of those cities are highly wired. Even if you discount the considerable rate of poverty (and I wouldn't, since video games have shown themselves to be eminently marketable within the disenfranchised segments of the population everywhere), those cities alone are a huge market boon. Ask any market specialist.
In my linkshell, at the point of the high population peak of the game, there were 15 (!) players that spoke English with some difficulty, and 12 of them lived in Latin America and spoke Spanish. 4 in Argentina, 5 in Colombia, and 3 in Puerto Rico (which might be an American territory, but has never stopped being a proud part of the Spanish Caribbean). That calculation doesn't include the many Hispanic/Latino American-born players in our ranks. Those numbers represent more than 10 percent of the linkshell population, and that is the case *without* a Spanish localization! Think of the possible population increase. And the enthusiasm of that population, given that it's mainly an MMO-virgin population just at the verge of becoming heavily penetrated. One in which the disastrous launch of v. 1.0 of FFXIV never registered... Most people think of China, the United States and Europe as the main markets that provided the gazillion players for WoW at its height... well, it won't surprise you that Blizzard knew they needed to translate their game to Spanish before they did so to French.
Do I need to go on...?