Hi Steve's! LOL and list: 

My Yaesu FT-450 has a Data USB and LSB mode setting. 
How ever, I'm currently operating remote and Ham Radio Deluxe doesn't have the Data settings, just RTTY USB and LSB. 
I tried both RTTY setting modes but there wasn't any change in the gibberish. The only thing is, I received an "overload" from the MTTY program, reported by the screen reader, when in RTTY/LSB so adjusted the RX control on my SignaLink until it went away but the gibberish still was spoken. 
The RTTY signals I'm listening to, are vary strong and clean so I don't see why there should be gibberish. I may have to play around locally and perhaps try my TS-570 until I get the text into spoken English. 
I do have my MTTY set to use the SignaLink as its transmit and receive device. I think that's working properly because of the scrolling, spoken gibberish and the fact that while listening with headphones, I also hear the rig transmit when I transmit. 
The SignaLink does transmit cause can see the transmit light and hear the device click to transmit and click again when it returns to receive. 
 

73: 

Michael DE VO1RYN