As far as ATMs go, I have never seen one in person. From what I've read about them, they don't apparently provide an anonymous means of cashing out bitcoin. OP, are you in Portugal or the US? There are ATMs scattered across the states, but I don't know about anywhere else. I haven't read much about them lately--there used to be a lot of threads about people using them and so forth, but it seems like they were mostly in Europe. I don't think they're catching on as much as people thought they would, just like bitcoin itself to an extent.
Be careful dealing with people on bitcointalk, because when you're selling bitcoin scammers come out of the woodwork offering PayPal and other reversible methods of payment, and they usually want you to send first. Always check people's feedback first. Good luck.
Tks to every single advise. I'm in Brazil, but I'll go to US soon.
After a lot of research, a lack of confidance in P2P transactions, and others factors, I'll try Localbitcoins or other decentralized exchange. Whatever.
https://coinatmradar.com/country/226/bitcoin-atm-united-states/
2-4% depends of the provider.
I'll lock this post. Tks for all the replies. If someone wants to write something down here, please PM me.