its a place where people speak polish and i will have to deal with a lot of people in restaurants, with cab drivers, hotel staff etc.
Restaurants and hotels will be fine with English, for cab drivers, use Uber (you'll need to download the app) where you order the cab through the app and they follow a route from GPS (so no cheating).
Of course some Polish phrases will be useful and I just googled 'survival Polish' and a few interesting websites came up. If you learn a few phrases, people will appreciate that.
If anyone approaches you after seeing this thread and offers 'lessons' by Skype, I would suggest you avoid.