form validation allow only english alphabet characters

I’d like to restrict my form input from entering non-english characters. For example, all Chinese, Japanese, Cyrllic, but also single characters like: à, â, ù, û, ü, ô, î, ê. Would this be possible? Do I have to set up a locale on my MVC application or rather just do a regex textbox validation? Just a side note, I want to be able to enter numbers and other characters. I only want this to exclude letters.