According to spreadsheet at KBA92442, 31250bps is supported (with perfect timing).
Question: Will PSoc Creator allow me to set this baud rate when I configure CY7C6511 on CY8KIT-049-4200? I haven't tried to do this yet.
You need to configure the USB-Serial device with the appropriate baud rate using the USB-Serial Configuration Utility present with the USB-Serial SDK. The Bootloader Host tool will allow you to set the baud rate when the device appears as a COM port before you start bootloading.
Please use external terminal option available in UART component configuration for 31250 bps. User can choose either an internally configured clock or an external clock for UART operation. Component configuration window will display the actual data rate based on the user-connected clock source frequency and the component oversampling factor selected.