The SAN CRC is a very pleasant place. The staff is especially helpful and friendly. I don't understand the comments about it being a bit of a hike to the DL gates. After clearing security it is midway down the terminal on your way to your gate. It couldn't be more convenient since you have to walk right past it anyway.

If your layover is more than 2 hours I would definitely agree with yngdiego and take a cab to downtown/Gaslamp or just Point Loma Seafood for a bite to eat.