Maybe I can help answer that question. I saw the english version with spanish subtitles here in Honduras. The audience that I saw this with consisted mostly of people who speak Spanish as their first language, but who also speak English well enough to want to see the subtitled version. While the spoken language was English, most all written words on the screen were in Spanish. My point is that the version we saw was still very much geared to a spanish speaking audience. When the spanish Buzz started speaking (in Spanish), the atmosphere in the theater changed noticably. The audience became alive. There was more laughter in the theater and the audience was more involved when Spanish Mode Buzz was on screen than at any other time during the movie. There was a real "connect" with the audience when it heard part of the movie in it's own heart language.
I asked an Honduran friend who took his family to see the Spanish dubbed version what he thought was the funniest part of the movie. He said that they (he and his family) thought it was really funny when Buzz started speaking Spanish. Now, for those who are paying attention, they were already listening to the movie in Spanish. Why would or how could he, and others, differentiate between the two. OK, here goes. In the dubbed movie Buzz speaks with common Spanish with a common accent. But when Buzz changes to Spanish Mode Buzz, his accent changes to an accent from Spain, which is quite different from Latin American accents. Also, he said, and I noticed this too, that Buzz speaks in a romantic style (I can't explain it, you just have to know). He also said that they enjoyed this part of the movie because Buzz was actually supposed to be speaking Spanish. In other words, Buzz was a Spanish speaking character as opposed to a character who is speaking in Spanish. I hope that makes sense.
As far as the music is concerned, he said all the lyrics to the songs were in Spanish. However, it's hard to say if the end credits were in English or Spanish. Usually, in Honduras anyway, the theaters here turn off the projector very soon after the credits begin. They do let the credits continue if there is some little funny thing going on in the credits, but when it stops they turn off the projector.
