something is chewing on my lettuce

Soap sprays may work. Good luck.

Try to determine what's munching on your lettuce before you attempt a solution. You may have a slug or snail problem, and a soap spray isn't going to be effective.

Slugs will leave a slime trail but you should look underneath the leaves for any insects. Sometimes wearing some gloves and squishing them works without the use of any insecticides. Remember you are going to eat your produce.

Could even be rabbits nibbling too.

I agree with StylishLady. Try a soap spray. If it works, it's a cheap and easy solution.

I used to put diatomaceous earth around plants which keeps snails and slugs away. Now, I just go hunting for the snails and toss them into an area which doesn't have plants.

Perhaps a Rabbit? lol

If you think it's slugs - buy harmless (to plants and animals) Slug-O and shake it around on the surface of the soil - slugs will retreat real fast.

I have not tried this yet, but I was told that if you like hot peppers, a habanero pepper spray will keep all bugs off your vegetables. You just blend habanero peppers with water, pour it into a spray bottle and spray your plants.

This also makes a good spicy salsa if you add a little salt. No kidding, we had this at a fish taco stand in Cancun, it was super spicy but so good on the fresh fish tacos. Waiter said that you can add olive oil instead of water if you want.

try some diluted Dr. Bronners peppermint soap. It has worked wonderful on all my plants!