Lindsay Lohan quietly turned 21 yesterday and spent the day at a beach house wearing a bikini and giant blue plastic shoes. Her mom and sister were there, along with friends Samantha Ronson, DJ AM, and Evan Ross. She left the party around 2:15 AM and went back to Promises where she's set to finish off her rehab. Allegedly no drugs or alcohol were served, but how else do you explain what she's wearing? Does she really want us ...