The only requirement for physical presence is after obtaining your conditional permanent residency. Opening your U.S. account will be dependent on your bank. If you are abroad, your interview would be at the U.S. consulate in your country.
During the EB-5 process which involves the filing of the I-526 petition and US Consular process of obtaining the conditional permanent residency, you do not have to be in the U.S. Depending on the type of EB-5 project you are investing in the Escrow account may already be established. Once you obtain your conditional permanent residency you need to intend to physically reside in the U.S.