I have a registration form with the new google recaptcha widget on it. When a user submits info, we check the validation with javascript and return the problems to the page
if you are using new recaptcha 2.0 use this: for code behind:
ScriptManager.RegisterStartupScript(this, this.GetType(), "CaptchaReload", "$.getScript(\"https://www.google.com/recaptcha/api.js\", function () {});", true);
for simple javascript