I work for the US division of Decca Records. First off, I'd like to say that you've built an excellent site. In regard to the Mexican soundtrack, I would just like to point out that in the liner notes of the CD it shows that the hispanic-flavored songs on the album were co-written by Silvestri and Abraham Laboriel, a renowned bassist and composer who was born and raised in Mexico City. So you were correct in your assessment that the song "OYE" was uncharacteristic of Silvestri's normal work. However calling the piece mocking is a going a little overboard. I think most people that have seen the film would agree that the song does an excellent job of supporting the fun and comedic atmosphere of that particular moment. If the song is mocking in any way it is of Brad Pitt's character. That small detail aside, you've written a very accurate and interesting review of the album.
Incidentally, you may be interested to know that we are planning relaunch our website sometime in the near future. The new web site will included a new and expanded soundtracks page. I hope that you and everyone in the score community will enjoy it