I've been looking around for Spanish-language websites and papers related to statistical analysis in football, and I've been able to find a couple.
The first is a Chilean/Spanish company called AIM Fútbol, which has developed a software package called SICO which generates advanced individual- and team-level statistics for professional football clubs. The company says that this work goes back eight years — I wonder if it's an offshoot of someone's thesis research at a university down there. (There are some good statistics and applied mathematics departments in Chilean universities, and one of them is truly world-class.)
The second is a Spanish website called Investigaciones y Estadísticas de Fútbol (Football Statistics and Research). It's centered around La Liga and has detailed data collection of goalkeeper performance and penalty kick performance (by players and goalkeepers). I haven't read all of the pages, but it seems that the purpose of the work is to prove why Iker Casillas is the most awesome goalkeeper in the world. I mean, he's very very good, but to me it's funny how almost all of the results go in one direction.
I also found a research paper, written in Spanish, that performs a regression analysis on the effects of altitude on match results in Bolivian football, while isolating for the comparative quality between the two competing sides and the home field effect. I'll comment on that paper in a few days' time.
Sé que esta página web recibe algunas visitas desde Latinoamérica y Europa, así que si conoces algún empresa o sitio que trata de la analísis estadística en el fútbol, por favor mándame el enlace. Y si haces investigaciones en el fútbol que quieres que reciba mayor difusión, mándamelas también.