a) Sorry !. As of July 2016, no ADRs from Ecuador ADRs trade on the US Exchanges.
b) Ecuador ADRs trading on the OTC markets:
1. Banco de Guayaquil (BGYQY) **
** This stock does not seem to trade.
Ecuador Dividend Withholding Tax Rates for US investors as of Jan,2016:
1.Dividend Withholding Tax for Regular Accounts: 0%
2.Dividend Withholding Tax for Retirement Accounts (401K, Roth IRA, Traditional IRA, etc.): 0%