I couldn't imagine being in a country for more than a few days and not speaking the primary language. My top priority the moment I learned I would be going there would be to become as close to fluent as possible.
I worked with a lady at Wal-Mart for a while who had been living here in the US consistently for decades, and still barely spoke English. I usually worked with her alone and trying to give her instructions or ask her to help with something was incredibly frustrating. We worked in the crafts and celebrations department, and she'd usually spend her entire 4+ hour shift rearranging and organizing the fabric and it was really hard to get her to do anything else.
Generally I would prefer to do so myself, for both reasons of respecting the local population and improving my own position while I'm there, but I won't condemn people who don't. After all, I cannot know their reasons for not doing so.
Also, I'd like to add a few 'weighing' qualifications. If I knew I was going to be somewhere for only three months, obviously I wouldn't learn the language to the same level as if I knew I'd be there for five years. Learning any language
well (let's say B2/C1 or higher in the CEFR system) will take a considerable time investment after all. Global importance of the language might be of interest, too. If I knew I were going to Spain for just a few months, I might invest more time into learning Spanish than into learning Georgian if I were going to be in Georgia (the country, not the state) - simply because Spanish in some form or another is spoken by a lot more people, in many more countries.
When I went to France for a few months on short notice, I chose to speak English in my working environment and French in all other environments. The reasons for speaking English in my working environment being 1) academic environment so level of English was comparatively high 2) had to communicate very intricate and technical issues precisely and 3) couldn't always reasonably expect my busy colleagues to take the time and patience to extract meaning from my insufficient French by querying on. Spoke French outside work as much as possible (informal meetings with those same colleagues or other groups of people, shops, wherever I went), to try to pick up as much as possible, only resorting to English when I found I really couldn't get my point across (and then asking how to say that in French). I guess I eventually would have switched to French in my working environment too, had I stayed there long enough. By the end of my 3-4 month stay I figured I could follow about half of what was being said between people, on radio and TV, my active language skills (speaking and writing) obviously lagging somewhat behind that.
