Hi Lyndon, You have to pronounce it with B. Spanish is generally pronounced as written. I sincerely hope this helps you, Lyndon. Have a wonderful day!

Please excuse this goofy comparison, but this is the equivalent of when Australians or New Zealand folks say Good day, mate. Sorry don't remember. But, to people outside, it sounds something like Guday' mate :)! It's just regional acceptances.

I agree with Fernando. You might hear that "buenos" is pronounced with a W or something in the middle, but that's the lazy (and incorrect) pronunciation, when we don't feel like moving our mouths too much :P So I think you should say "buenos" with a plain B :) Regards.