Should you host the site there where your customers are?

From the point of the potential customer, a site hosted relatively local to that customer may have slightly better response (page loading times) than one halfway around the globe, but apart from that, there isn't much difference from "our" perspective. Given the speed of the inter-continental connections, it is unlikely that most customers would notice the difference, unless there are significant internet traffic issues between the foreign location and your US based servers.

However, from the perspective of Google, they may "appreciate" or "prefer" to see the site hosted in the country when it comes to ease of classifying sites for "local search" options. They may give you a better page ranking on local search results as a result. This is conjecture on my part because I don't have any foreign language pages that I could use for split testing.

As far as personal preference goes, unless I could prove a clear benefit to either the potential customer in page response times, or verify a Google ranking algorithm that gave me higher rank for locally hosted pages, I'd keep the site (pages) on a US provider that I'm familar with than go to an alternate somewhere else, especially if this is a foreign language version of english content on the same web site.

For performance, you could cache resources on a Yahoo S3 or cloud service node closer to your visitors, the wordpress w3 super? cache works with S3/Cloud. the yahoo costs may be negligible, they give you like 15 gigs a month free for the first year.