How to change "New content" text in entity connect autocomplete edit/add buttons?
In a form alter you can access those two buttons with something like:

$field_name = "field_test";
$form[$field_name][LANGUAGE_NONE][0]["add_entityconnect__".$field_name."_0_"]["#value"] = t("New");
$form[$field_name][LANGUAGE_NONE][0]["edit_entityconnect__".$field_name."_0_"]["#value"] = t("Edit");


Adapt the name, language and cardinality of the field accordingly.

You can use a basic hook_form_alter to affect all forms. The widget creation code is in entityconnect.form.inc and it can't be altered (no hooks, no variables).