Using a hose to wash the bike off is not a problem-- Power washers are though. Depends how muddy it is and how dry the mud, but I have a power washer that I use on the bike, but nowhere near any form of Bearing or orifice where a lot of water getting in will cause damage. By that I mean around the gear changers or pedals.

Main thing is to spray with water displacement lube after wards (WD40, GT45 etc) . The whole bike gets sprayed except the brakes, saddle and grips. A couple of hours later the bike is wiped clean and chain and cables lubed. Then it is ready to get covered in Mud again next time out.