Hop on the 5 south to the 55 south to the 405 north.
From the 405 north exit Beach Blvd south and drive (several miles) until you reach Pacific Coast Highway (PCH). You can't miss PCH. Well if you do, you'll end up in the water.*
Turn right on PCH and drive until you reach Main St. (Not very far).
Depending on when you leave, it should take you about 30 minutes to get there from DLR.
There is a parking structure off of Main St that you should park in. Metered parking is a ripoff and the restaurants validate for the structure. You can also valet park at Dukes/Chamyos which is at the end of Main St (you'd turn left instead of right...you'll see it). They also have day parking for $7 or $10 around the beach.
Be careful when driving on PCH, and Main St, the cops love to ticket speeders and those who fail to stop at the stop signs.
Rubys is good, as is Freds Mexican Cantina and Dukes.
*If you want to drive down PCH longer than a mile Exit Brookhurst South instead of Beach Blvd. and take that to PCH. Turn right on PCH. This will give you about 3-4 miles to drive on PCH.