If you can provide an example of such a diverse set of languages becoming a new language, that would be interesting.
Creole has nothing to do with the number of languages. Creole is what you get when two groups of people with no bilingual speakers are forced to interact and develop a new language. Normally, it starts as a pidgin to facilitate trade but then develops into a full fledged language. The main difference with Spanglish being that the speakers often know both languages to a modest degree but probably would not be considered native by other native speakers. Also, there are almost 1M Dominicans alone in NYC. 20k makes it sound like some cute phenomena happening in Little Havana in Miami.