The B-1 business visitor visa is not for visiting a Regional Center which will lead to Green Card. However, if you’re in the US as a B-2 tourist, there is nothing wrong with side trips to visit Regional Centers as long as the primary purpose of your trip is tourism.
This is a valid purpose for a B visa. A Business Trip.
When I was in Vietnam, this past November '11, in both Hanoi and Ho Chi Minh, I accompanied some of our prospective investors to the (state department side of the) Embassy in Hanoi, after they were denied non-immigrant visas to visit an EB5 Project.
I spoke to the Head of the State Department side of the Hanoi Embassy, and he explained certain "red flags" they look for when issuing non-immigrant (tourist, or business) visas to visit the U.S.
It is not impossible to obtain a Visa to visit the U.S. for the purpose of Due Diligence of an RC or EB-5 Project...
However, you must clearly document your financial and property ties to Vietnam, along with your previous international travel.