The MB aquarium isn't bad. I've been there many times, and in fact, helped build the "Outer Bay" exhibit when they expanded about 15 years back.
Bring a warm jacket. When the marine layer rolls in during the evening, it can get cold as hell there...and wet. The fog can be VERY thick sometimes. We went to Monterey for the 4th of July in 2003. It was kind of cool watching the fireworks in the fog. Most of time, it was just a sudden burst of color in the fog, rather than the bright explosion of color that you normally get with fireworks displays.
My favorite restaurants in Monterey are:
Hula's (on Lighthouse near the aquarium) small place-great food-Hawaiian cuisine
Bubba Gump's (cannery row, near the aquarium and right on the water-good seafood-Forrest Gump atmosphere-fun if you've never been to one)
The Breakfast Club (on the hill on Fremont street IIRC-used to be the best breakfasts in town-great food-huge portions)
For a first-time tourist, Santa Cruz can be fun. Lots of female bodies to look at, some decent food available on the pier, great roller coaster.