How viable is the Star Wars model of intercultural communication?

Multilingualism is extremely common in many regions - people speak several languages in addition to a possible lingua franca or several Lingua Francas - which is not always English or even not mostly English. For example, in many areas of the Amazon, people will speak Portuguese as the main Lingua Franca for communication with officials, an indigenous Lingua Franca for trade and other interactions and one or two other local languages (often as a result of intermariage). This all happens without any major investments in the educational system. However, remember that this multilingualism does not mean that these people have native-like command of all of these languages. Further, in amongst these multilingual people it is not uncommon to find many monolinguals who are very insulated from others.

However, the modern nation-state-induced monolingualism is not only way language skills are configured nor is it the norm.

PS: I don't think the linguistic aspects of the Star Wars universe are sufficiently well elaborated to build a model on them. There are more linguistically realistic universes out there (Tolkien being the high mark in this respect).