The widgets give warnings as soon as the guest clicks the Book Now or Send Inquiry button. We don't do it inline as data is entered as guests will often adjust things, and also because the rules are very variable depending on dates, so they need to be executed separately for each set of dates.
When they click the button, three steps happen:
1 - input validation is done (email entered, etc). Errors are displayed if they exist.
2 - if input validation passes, run the rules engine based on property and season rules. Rule errors are displayed if they exist.
3 - if both validations pass, the inquiry or booking process is started.
For example, on your widget, you'll see the following: http://imgur.com/a/Gpus3 if you were to submit with those values.
