The best examples that come to mind are when ordering food. As examples:
• You speak English and Spanish and are ordering a burrito
• You speak Thai and English and are ordering Tom Yum
I imagine it could depend on numerous things:
• You primary language or ethnicity
• What sort of restaurant
• Who you’re dining with
• Who you’re ordering from
• and probably a lot more…
I use the language that I think my interlocutor would prefer. If I don’t know, then I default to the language of the social context, unless I specifically want to practise a language at that moment. If I want to practise, then I ask first.