Can we pronounce the English letter "z" as "j"?
In Bengali, the sound "z" does not exist. People who have a lot of contact with English or other foreign languages learn to pronounce the "z" sound properly, but the rest approximate it with the sound of "j". So it's not uncommon to hear the number "zero" in English being pronounced something like "jiro" among Bengalis. It's an approximation, and it works.
Depending on the level you're trying to attain at this stage, it may be perfectly reasonable to approximate the "ভ" sound with "v". People will have no trouble understanding you.
If your question is about writing you can write bhalo or valo either way. Nobody cared enough to make a romanization system for Bengali writing. So everyone writes them in English as they feel.
If you want to know the correct pronounciation it is valo (bhalo), not balo. Although people will excuse you as a beginner or non-native speaker, you will sound like a toddler if you make the b sound instead of v.
Depending on the word you use "V"
Example:
Good = ভালো ; you can use either V or Bh for this one.
However, for Beggar = ভিখারি you can use V, it will have to bh.
Best practice is using bh always for not to get confused.
