Andy, this is possible, however you need to monitor your hotspot to check whether it reached the full capacity or not.

Whenever you want to temporarily disable new registrations, just go to the Control Center, click on Manage > Locations > click on the name of the location > Modify Hotspot Data > Splash Page Settings, uncheck both the primary payment module and the paypal module.

That way your customers will see a message saying ‘the location is currently not accepting credit card payments’.