It's hard to say, everyones different, but the conversion to L-dopa is slow, most might be digested before being converted to L-dopa, which is why L-dopa is the one used medically. Even most L-dopa doesn't become dopamine in the brain, it has to be combined with carbidopa. Your body make it's own tyrosine, and dietary protein also has a lot of tyrosine. It might not be that effective compared to l-dopa. That's the problem with dietary supplements, they can make claims they don't have to back up with research.
For a healthy person with a decent diet, their might not be a need for tyrosine or L-dopa.I tried doing something similar with 5-HTP and ecstasy, just converted to serotoin in my gut and gave me an upset stomach.