Whether you're at a lanchonete counter or a restaurant table, a handful of phrases will carry you through the whole meal:

Portuguese	English
O cardápio, por favor.	The menu, please.
Eu queria…	I'd like…
Pode me trazer…?	Could you bring me…?
Para mim, …	For me, …
Mais um / mais uma, por favor.	One more, please.
Está delicioso!	It's delicious!
A conta, por favor.	The bill, please.

The waiter is o garçom, the waitress a garçonete. Water comes com gás (sparkling) or sem gás (still). Pode me trazer is built on poder (can) — for now, learn it as one block.