Indeleta, I used 2X10 Douglas Fur for my beds. But cedar would be much better and last much longer. Does anyone sell 2X12 cedar near you? Not having a gap between two boards would likely make them last longer.
Depending on your height you may want to go less than 4' wide. My first beds were all 4' wide. Then I built trellises by attaching 2X4's on the outside on both sides. The center of beds were just a bit out of reach from all side when I was done. And any tomato or fruit that was dead center was not easy to get. I could touch, but could not grasp. For now on I will be building my beds 3' 6" wide.lol