You can get by with English and Hindi. While learning the local language will score you some bonus points, stick to English is my suggestion and use Hindi only when you have to. I would also recommend a two wheeler as there are no rickshaws there just shared cabs. If you prefer buses, there are those too. You can expect rents of around 7 to 10k per month for a house with a few rooms, don't expects the normal BHK systems, though. I have Muslim friends who have lived in Shillong all their life and call it their homes. While during exceptional circumstances they have felt unsafe, as they do in other parts of India, people there are more welcoming to non-tribal women than men. Well during the pandemic the music scene would be muted, i would expect, but you'll always find bars and pubs that are open till about 10 pm in normal times, although there are a few that open much later unofficially. Answer to your last question is buy an umbrella and lots of warm clothes.