I can see the argument for calling it laziness, but I see it also as inventing a whole new language as one goes along, with a certain set of tools at hand. Personally, I find it fascinating to listen to, and occasionally hear things expressed in Spanglish much more colorfully, or powerfully, or succinctly than either language alone could do. It's also fun.

I am very familiar with Spanglish and as you say, it is fun. It is also much more than that. When two cultures meld, there are experiences in each culture that have no easy word groupings to describe them in the other language. It isn't a question of laziness, but of being precise in the wording. It is such a relief when one is talking to someone of a similar mixed culture to use the proper words to describe each situation and know that you are perfectly understood.