When exactly should u get tested for aids soon after having sex in foreign country?

At 1st chance. It is a good idea to get tested at the first place that does it, like in the U.S. At a hospital near you. It is also good to follow up after the testing, because you cannot be sure when the first exposure really was, or to whom. This is something that should be maintained if these activities are going to be kept up, and not just for hiv, but for other diseases.