Mountain bikes (and other types) commonly are splattered with mud, dirt, sand, and sometimes even manure. Cleaning an entire bike by hand may take a while, and hosing it down completely would soak the seat and handlebar grips, requiring time to dry. IN this case, you can take your newly cleaned bike for a ride seconds after washing.
Carefully and neatly, wrap one or two layers of plastic bags around your bicycle's seat, handle bar grips, or anything else you don't want wet.
Using an elastic or tape secure the wrapped parts.
Then lightly hose the entire bike with a commercial grade garden hose, until clean.
Use old worn-out socks or clothing to rub the dirt and grime off.
Bounce the bike up and down on the tires a few times to quickly shake off the water. Watch for any loose parts or cracks in the frame that need repair. You can spin the cranks and pedals backwards to spin more water off the chain.
Afterwards, remove the plastic bag coverings and let it sit in a warm and dry, preferably sunny location to dry. You may dry and reuse the bags.
Remember to re-oil the chain once it has dried or before your next ride. Wipe off the excess oil with a discarded sock or rag. This will help to avoid rust and keep you riding FAST!
Enjoy your clean bike that's already dried and lubricated for riding!