For art (signs go under that for me) i would use a vector graphic program for the design. Paid -> Illustrator, free -> Inkscape. Simple programs to make the g-code out of .SVG are Easel, Carbite Create or MakerCam (Flash, so not recommended, worth a try is KrabzCAM, generate g-code from svg). For precision works where parts have to fit together, CAD/CAM programs like F360 or FreeCad are recommended.