I use to go to a small dive shop on PCH, on the northern side of Laguna Beach. It's well equipped, and they can give you pointers to where the best dive spots are located.
I lived close to Hermosa Pier for several years so that has a special place in my heart, but I really like the whole Strand from the Redondo Beach Pier up to Manhattan Beach Pier.
And Manhattan Beach's night scene is picking up a bit over the past year or two. It will never be the same crowd as Hermosa but I think Manhattan has a decent share of good restaurants and bars.
Laguna Beach used to be my favorite, but it seems to get too busy now. At least most people have not found my secret parking lot. Although it is usually 70% filled every time I go now versus 10% filled when I used to go in the 90's.