My favorite morning or evening casual ride around South Beach starts at the south side of Alton Rd & 5th street and stays along the water until the bike path turns into a pedestrian only path up past the W Hotel, about 21st and Collins.  It's just over 3 miles of waterside riding along the Bay, the inlet & the Atlantic Ocean.  I suggest morning or evening because I prefer not to have to dodge too many pedestrians, and I always start at 5th because my favorite approach to the Atlantic is along South Pointe Park, where if you time it right, you can ride along as the sun, or full moon rises,  Evening is especially magic when the cylinders of light, that are the inlet markers, light the path with a modern art glow.  Be careful of the waiters crossing your path by Smith & Wollensky! 

Start the ride on the pathway along 5th toward the bay & stay on the bike path!   There are a couple of spots where sand riding is required; if you're bike has serious road tires, you'll need to cut along the street for a couple of blocks before you hit Lummus Park.  Lummus sits opposite the Art Deco hotels, where there are lots of sights and great food to enjoy.  You can also take some variations by visiting Espanola Way  (turn off the path at 14th at the end of Lummus, then go right one block on Washington and left on Espnola), or you can visit Lincoln Road and all the shops & eateries there by exiting along the Beach Access next to the Ritz Carlton. 

For those without bikes, you can rent an Art Deco bike at 4th and Alton (West side of Alton across from Publix) as well as many other places.  You can check out the locations here:  www.decobike.com

or you can rent a bike for the day at miami beach bike rental, great family run place that does an escorted community ride the 2nd Saturday of every month!  You can check them out here:http://www.bikemiamibeach.com/

Enjoy the ride!