You could override the jQuery.validate.js
script, but it will add permanent dependency to globalize.js
find this:
return this.optional(element) || /^-?(?:\d+|\d{1,3}(?:,\d{3})+)?(?:\.\d+)?$/.test(value);
and replace with this:
return this.optional(element) || !isNaN(Globalize.parseFloat(value));