Yes, no, thank you and please are a good start. But as mentioned, most cast members speak English and the language is not as much as an issue as it could be a few years ago.
How many in your party you can always do with your fingers, depending on the ride, some can be loud, like Pirates and BTM. These are the only rides where I have a preference to sit at the front (Pirates) and back (BTM). And I always ask in English.
I wouldn't exchange money, unless you plan to buy at a mobile food cart. In the summer they add extra ice cream carts which don't except cards. I would pay everything with card and if you really want to buy something that needs cash, I would go to the ATMs around the park. But of course depends on your bank if there are extra costs (it's not the case for my cards, only for cash withdrawal).