It could be any number of pests and without seeing the type of damage it is impossible to say for sure. Mice is surely a possibility but so are rabbits, groundhogs, slugs, and even caterpillars or worms such as armyworms or loopers. Even deer if they have access to your area.

A photo might help narrow down the possibilities.

Dave

Snails?

Having lived & gardened in SoCal, my two best guesses would be snails & cutworms. Snails would leave a trail, and you would find them hiding under cover during the day, such as nearby landscape timbers or garden debris. Cutworms hide by day in the soil at the base of the plants... if you gig in the loose soil surrounding the stem, you will find them.

Fast fingers got the best of me. I meant to say: "...if you dig..." :-0

Could be rats or worms. What about pill bugs? Do you have a lot around?

I tried uploading some photos but couldn't get it to work. Anyone knows how? I looked under the leaves and didn't see anything. I also don't see snail trails plus I put down some snail bait a couple of weeks ago. That could use some refreshing I'm sure but I think I still would see some trails, no? Since I couldn't find pests on the leaves, I got a general pesticide (sorry!). The next day, I saw that whatever this thing is again attacked my plants. This time, they didn't devour the leaves but left lots and lots of little holes. Looks like someone took an insect-sized shotgun to my broccoli leaf.

That sounds like flea beetles.