Without even running your code, I guess that you made an error lot of newcomers did: you forgot to put a background() call at the start of draw(). Thus you cumulate the text drawings on the same place, destroying any anti-aliasing that can be made. Adding smooth() in setup() can help, too.

Ah, yes, you are in 3D. So you need to add textMode(SCREEN):

1. void setup(){
2. size(600,600,P3D);
3. fonty = createFont("Arial",18);
4. smooth(); 
5. textMode(SCREEN);
6. }

Note that this mode, and P3D, will disappear in v.2.0...

OpenGL. There are note on the incoming new version on the Wiki.