1st, I need to know. Are you using 32-bit or 64-bit?
2nd, the MATE desktop environment runs great under X2Go. But if you are using the Cinnamon desktop environment, I am not sure if the version of Cinnamon in Linux Mint 15, 1.8, is compatible or not. I think it is, I'll test it before I upload the packages for you. I recently tested 1.4 (Linux Mint 13) successfully and I think that I recently updated the logic in x2goserver to accommodate the filepaths for Cinnamon 1.8.
I was not able to get Cinnamon to work under Linux Mint-Mate 17 over
x2go. It well may be operator incompetence however.