You can get to Caen taking inland or coastal roads.  I prefer the coastal route.

The Coast

Take the D513 to Cabourg; turn off to the 514 to Merville France and through what looks like forgotten villages.  Although the D514 is close to the coast, you don't actually see the sea.  You'll get to the D515 which has a 110 km speed limit and no shoulder for bikes--so get off at Benouville, turn to the left (Benouville parc) and you will see a little opening to a little bridge that will get you on a bike road along the canal all the way to Caen (about 12km).  I stopped for the cheapest cup of coffee anywhere in Normany in a lost hotel/cafe along this road.  (The price of coffee decreases as you get further from Deauville.)  The wide canal view is lovely, but sometimes marred by views of storehouses and grues on the opposite side.

Inland Road

	Take the D27 either from the D278 (at the round-a-about out of St. Arnoult) or from the Trouville-Deauville-Touques intersection at the N177 (D677) towards Tourgéville.  (See details on my Troarn page.)
	Stay on the D27 all the way to Varaville.  Most of the D27 has open views and traffic should not be too heavy.
	At Varaville the D27 ends as it intersects the D513.  Turn left unto the D513 in the direction of Caen.
	You can either go to the center of Caen by staying on the D513, or turn off unto the D224 towards Ranville where you can go on to cross the bridge to Benouville and then turn left unto the 514 towards Ouistreham instead.
	If you go all the way towards Ouistreham and meet the sea, you will find yourself at the very edge of the Plages du Debarquement (here specifically--Sword Beach) where the Allies landed during WW2 and saved the world.

The Route Home

	Don't dare rush home before visiting a few truly wonderful chocolate shops you can find only in Caen: Temoins, Charlotte Corday, and Hatot.  Remember that this is France and most shops close for lunch (12:30-14:30) so plan your trip accordingly!
	Take the D513 all the way home, passing through Cabourg and following the coast home.  This is the most direct route and took me 1 hour 50 minutes at a comfortable pace.