But this wasn't his question. If he has what it takes to get really good at C++, he will probably get really good at Ruby or Python in that time.
I happen to work in a place where we use Python and C++, and I claim that for any problem domain for which higher level (lightweight?) languages are suitable, they are a clear productivity win over C++, for people of similar experience.
I agree that people are more important than language, but the choice of language also tells you something about the people. I suppose the poster has more relevant information about the people, though.
Remember, that when it comes to programming language choice, you often end up with programmer happiness (low ramp-up time to get something implemented) vs. performance.
It would be good to find out how open the place is to different languages. You may be able to write most of it in the language of your choice and only have to switch to C++/Java where necessary. This should especially be true at a Web-focused company.