Should I try to learn the local alphabet?

Only if it is a different script (like Japanese or Greek). Learning the basic characters for 'exit,' 'toilet,' and 'train' is high-value; trying to learn cursive script is a waste of your time.

Will people just switch to English immediately?

Often, yes. But initiating a conversation in the local language—even poorly—shows respect and usually results in much better service.

It's good for habit building, but it is too slow for travel preparation. Use it as a supplement, but focus on direct 'survival' phrases instead.

How to learn basic local phrases before your trip

Focus on the 'Big Five' categories: greetings, ordering food, asking for help, numbers, and basic courtesy. Dedicate 20 minutes a day for at least two weeks before departure using spaced-repetition apps rather than traditional grammar books.

Identify your essential vocabulary. Don't try to learn a language; learn a survival kit. Write down 50 phrases: 'Where is the bathroom?', 'How much is this?', 'I'm allergic to nuts', 'One water, please', and 'Thank you/Excuse me'.
Use Spaced Repetition System (SRS) apps. Download Anki or Memrise. Use pre-made decks for 'Travel Survival [Language]' to ensure you are practicing the most common words instead of abstract concepts like family trees or colors.
Practice audio input exclusively. Listen to Pimsleur or Michel Thomas audio courses during your commute. Travel language is about speaking and hearing, not reading. Your brain needs to recognize the sounds before you can replicate them.
Create 'cheat sheets' for your pocket. Write your core phrases on a physical index card. Keep it in your wallet. Even if you don't use it, the act of writing the words helps commit them to muscle memory.
Master the 'bridge' words. Learn how to link words together using 'and,' 'but,' and 'or.' This allows you to construct basic sentences even with a very limited vocabulary.

Should I try to learn the local alphabet?: Only if it is a different script (like Japanese or Greek). Learning the basic characters for 'exit,' 'toilet,' and 'train' is high-value; trying to learn cursive script is a waste of your time.
Will people just switch to English immediately?: Often, yes. But initiating a conversation in the local language—even poorly—shows respect and usually results in much better service.
Is Duolingo enough?: It's good for habit building, but it is too slow for travel preparation. Use it as a supplement, but focus on direct 'survival' phrases instead.