I was very amused when I read the section with the Argentinians. I thought the "Gaucho Marx" comment was hilarious and the name U.S.S. John E. Badass sated my desire for some cheap humor.
I loved use of Spanish. Previously, when Pynchon used German and Russian, I felt lost (especially because I don't have that companion book). Finally, I am relieved that I at least can understand SOME of the foreign language represented in GR. I really appreciate Pynchon's knowledge of languages now; he describes the Argentine Spanish both descriptively accurately and artistically: "The conversation in the steel space that night was full of quiet damped ss and palatal ys, the peculiar, reluctant poignancy of Argentine Spanish, brought along through years of frustrations, self-censorship, long roundabout evasions of political truth- of bringing the State to live in the muscles of your tongue, in the humid intimicy just inside your lips...pero che, no sos argentino..." (390)
I agree, I think it really adds to the novel (and its "encyclopedic" characteristics) to have these foreign languages adeptly strewn throughout it. I was also impressed with how well Pynchon uses each language's nuances (or at least, how he used French, since that's the only other language I speak) to describe things in a much more effective way than he could have done in English. For me, it also helped add to the book's "authenticity" (i.e. Spanish comes up when talking about Argentinians, French was spoken in the Riviera, etc., which seems much more realistic than just using English all the time).
I liked how he used the Argentina-specific "che" and "sos" too. I think it contributed to the overall characterization of the expatriates and, I'm not sure where I'm getting this, but it also seemed to lend a sad undertone to that whole subplot.