Yes, I could solder it on one side, but it wouldn't look that nice. I have jumper wires, but I would like to have it fixed on the breadboard, not lying around on a cable.
As far as I understand, I would get 10 PCB for 10$ (+ shipping, making it about 10€) from Seeedstudio. So cost is not an issue, neither is a bit soldering.
Apart from that, I am really interested how the order comes out. I would just appreciate if someone would confirm that my layout is technically correct, as I have no background with PCBs.