Depending on the current draw, you may be better off with a low-dropout regulator (eg. LM1085IT-12) for this as the power loss as a result of the voltage drop will essensially be 13%, but if you are not taking much current then that's the loss you'll get with a typical DC/DC buck converter.
Some loads such as motors and even some equipment like decent routers/modems/switches can actually handle the extra 1.8V too, so if your load can cope with it, then it is a good idea to omit the LDO or DC/DC converter.