Yes, one can be open to hear about job offers or complete interviews while on visitor Visa. There is nothing wrong with that activity. If you get an offer then their "letter of offer" then gives you ability to apply for an official work visa, which I'm certain you don't have to leave the country to do. But I do hear for some reason it takes longer to process if you are in country (4 weeks average) vs. out of country (5 days average). But most jobs know one can take 2-3 weeks average to be ready to start a job.

Also, the job offer has to be from an accredited employer, I believe, for all offers. You can ask if they are accredited already with the government, and if not, they can get on the immigration site to get accredited. That doesn't cost them much and can average to take 10 days to complete for them. But if you get an offer from an accredited employer it won't take long at all to start.