This summer, leave the car in one place and take the free Summer Beach Shuttle from Playa Vista to Marina del Rey and then Venice Beach Pier. It's free weekend transportation, running from about 10:00am to the evening hours Friday thru Sundays, and holidays as well as certain Thursday evenings when there are the free Concerts in Burton Chace Park. Go to Fisherman's Village, many of the restaurants along Admiralty Way, the hotels and even the Venice Pier, restaurants and shops on Washington Blvd. as the bus takes a loop back to Playa Vista. The buses run every 30 minutes or so, are wheelchair acessible and are equipped with bike racks.
During the Summer months, on the weekends (Fridays thru Sundays) and holidays, leave the car in one place and take the Marina del Rey WaterBus to the various areas of the marina. This "water taxi" takes riders from one side of the marina to the other via the water -- go from Fisherman's Village, to Chace Park, to the Waterfront Walk and the restaurants, Marina (Mother's) Beach, for a total of seven boarding stops. The fare is just $1.00 each way, and bikes and strollers are welcomed. The WaterBus also runs on Thursday Concert Nights from 5:00 pm to midnight.
There are buses that runs into and out of MDR/Venice/SM areas. Bus fares are I believe $1.00 - $1.50. Let me throw a caution however, if you take the bus, then you will actually miss the beef of your travel since most of the activities are located close to the beachfront.
I would suggest renting a rollerblade, a bike (single or tandem), or just walk...This way you're right in the thick of everything.
If you take a car, be prepared to pay $20.00 for a parking space - if one is available.
One can drive there but it's more fun to sail over like this goofy guy in the green shirt is doing! Picture from mid 1908's.