I can see that Parsley.js handle English separators for numbers.
When I use Parsley with Spanish numbers it doesn't work (example : 5,50 is not a valid number for Parsley and in my country comma is our decimal separator).
Is there some config to change it?
You need to create the necessary regex that matches your needs. A (probably rudimentary) regex would be ^\d+(,\d+)?$, that matches any digits or digits with commas.
You don't even need to create a custom validator, since Parsley allows you to use data-parsley-pattern which receives a regex.
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/parsley.js/2.0.7/parsley.min.js"></script>
<form data-parsley-validate>
<input type="text" name="commaNumbers" data-parsley-pattern="^\d+(,\d+)?$" />
<input type="submit" />
</form>