How do Brazilians use valeu?

Brazilians say valeu for a quick thanks, often with a little extra: Valeu! on its own, Tá bom, valeu! ("OK, thanks!"), or Valeu pela ajuda ("thanks for the help"). These are lines from the course:

PortugueseMeaningIn CiaoSpeak
valeuthanks (casual)Unit 2
Valeu! Até mais.Thanks! See you.Speak: Ride-app car
É, você tem razão. Valeu!Yeah, you're right. Thanks!Speak: New job
Ai, valeu! Eu vivo perdendo essa chave.Oh, thanks! I'm always losing this key.Speak: New job
Quero, sim! Valeu!Yes, please! Thanks! (your answer at a beach kiosk)Speak: Beach kiosk
Valeu pela ajuda!Thanks for the help!Not in the course

Is valeu informal?

Yes, valeu is informal, but it isn't rude: it's fine with friends, coworkers, drivers and people your age. With older people, in a formal setting or in writing, obrigado or obrigada is the safe thanks; see how to say thank you in Portuguese.

Who you're talking toCan you say it?
Friends, people your ageYes
Coworkers, drivers, the person at the counterYes
Older people, your boss, a formal emailBetter obrigado / obrigada
PortugueseMeaningIn CiaoSpeak
obrigadothank you, said by a manUnit 1
obrigadathank you, said by a womanUnit 1

Can valeu mean bye?

Yes: among friends, Valeu! or Valeu, falou! closes a chat or a call, like "thanks, see you!". It can also mean "OK, cool" after someone tells you something.

PortugueseMeaning
Valeu, falou!Thanks, see you! (very casual)
Valeu, até amanhã!Thanks, see you tomorrow!

How can you practice Brazilian Portuguese out loud?

Practice it in short, real exchanges, out loud. CiaoSpeak's Brazilian Portuguese course teaches everyday words like valeu with a recording in a Brazilian accent, and in the Speak tab people across Brazil (a São Paulo baker, a Rio ride-app driver, your language-exchange partner Ana) ask you one question at a time. You answer by voice or typing, and the app tells you whether a Brazilian would understand you. Lessons are free; in the Speak tab, today's questions (up to five a day) are free too, and CiaoSpeak+ adds practice in any scene whenever you like. More words like this one: the Brazilian slang list.