Yes, there are many reports and screens on which you can send mass texts to customers.
Advanced Search
A great place to send bulk emails and texts from is the Advanced Search. Go to Customers->Advanced Search->Filter for the customers you want to send a text to (e.g. Inactive customers), then hit the Actions button at the top of the report->Send SMS
Route->Calendar
You can send a bulk text to everyone on a route from the main calendar page by 1) clicking on the route name, 2) clicking on the Action button, and 3) hitting Send SMS.
Route->Reminder
(and almost all reports that pull up a customer list)
If you pull up a report and there are select boxes next to the customer's information, chances are you can send bulk messages to the selected customers. First, select the customers to whom you would like to send a message; second, scroll to the bottom of the report; third, hit the Send SMS button.