Yes... You can flip the direction of axis movement by changing those #define's. But make changes carefully. Check them out with PronterFace and be ready to press the Reset button! The problem is you also have to have your limit switches #define'd correctly. So, if you get things to move rationally with PronterFace, you can use the M114 command to verify the limit switches are detecting the end of travel on a given axis.

That is a very nice looking printer! I wish my printer was made like that.