We rented a pair of beach cruisers at Marina Bikes recently. We found the price to be right--they tally your time when you return the bike, so you don't have to commit to a specific time period--and were delighted with the wide bike lanes available on that stretch of Harbor Drive. There is good access to The Strand, both south toward Torrance and north toward Manhattan Beach and ultimately Santa Monica. We brought our own helmets and gloves, but took advantage of the shop's optional (for no extra charge) bike baskets and locks. If you're in the Beach Cities, this is a great option.
Pros: reasonable prices, good beach access