Critter Ridder is really nothing more than expensive red pepper. It could get into your cat's eyes and that is cruel. It also doesn't really deter anything that well.
It will only stop them from digging a little bit.
Cat's don't like rough or pokey things on their paws, there must be something else you can cover the soil with that doesn't stop water getting down in or hold too much water in or harm your plant in anyway.
They might not like the scent of mothballs...but then you wouldn't either. Just remove when watering and replace.
Or maybe some chicken wire cut into pieces and laid on top. I don't have a cat so don't have the problem, maybe others have some ideas for you.
Call a pet store and ask them.

About your PL, Are you watering from the bottom? If so perhaps the entire rootball is not getting enough and the roots are searching for more water. It does sound like it needs repotting but you can only tell if you remove it.
If it needs repotting and you don't, it will probably slowly decline and eventually the pot will be full of roots and little soil as it breakdowns and washes out.
What size of pot was it in?
What size did you repot it into?
Sometimes IMO most plants bought are needing to be repotted.

Shannon, I used to sprinkle Cayenne Pepper around the rim of containers. Afterwards, when my cat, Hallowen, approached a plant, (he had a few favorites) he detected the Cayenne scent, and quickly made a U-turn. Thankfully, there were only 2 or 3 plants he liked, so after sprinkling the Cayenne, he stopped. Citrus is another scent most cats would rather not deal with.

For large pots, 10+" diameter, this is what I ended up doing.
I had a Dracaena 'Corn Plant,' in a, I believe 12" pot. My cat, Halloween, decided to use the canes as scratching posts. I cut a piece of cardboard in half, then cut out circles where the canes grew. Set halves together so it looked like one piece. When he jumped on the cardboard, because it wasn't glued down, it started shaking. Halloween immediately jumped off the plant..The cardboard resolved the Corn Plant problem.

How many kittys do you have? I bet they're adorable. As long as their liter box is kept cleaned, even if that means daily scooping, they shouldn't 'go' in a plant pot. But kittys are strong-headed.
Are they nibbling on any of your plants? If so, perhaps you can either buy kitty-cat plants or grow your own.

Shannon, if roots are sprouting from the drainage holes, your PL is probably root bound or on the verge of.
If you can answer Goblue's questions about pot sizes it'd help. There's different types of PL's, some dwarf some grew quite big, with gigantic leaves. Did your PL send out more growth since April's repotting? Toni

Shannon, we have two full grown adult kitties who are very stubborn and set in their ways so I understand the frustration you must be feeling to have yours use your pots for their litterbox. (sigh) What I do with pots and every where else I don't want ours to go is to place duct tape sticky side up around the rim of the pot or across the top of the pot in the form of a grid. When ever "the boys" perch on the rim of a pot, they definitely do not like the sticky feel of the tape and skeedaddle right out of there. I even use the tape method on table tops, stands, and shelves - anywhere I want
"the boys to avoid". On one occasion one of the boys got a small piece of tape stuck to the bottom of his foot and it was very entertaining to see him trying to walk and shake it off! LOL.

Gob~ I'm not too keen on the thought of moth balls... They stink! Of course, so does kitty doo-doo! :) I've thought about chicken wire, as you mentioned... I think it would be easy to work with & easy to take off when the plants come back inside for the winter.

As for the PL, I noted in my OP that I didn't water from the bottom, but drench it w/ the faucet in my sink or shower, so I don't think the roots are looking for water. It was originally in a plastic insert inside of a tin decorative planter... This is why I repotted it in the first place, b/c the original container was not condusive to good drainage. I repotted it in an 6 in. pot... The root ball only had about 1 in. on the sides that I had to put new soil into, so I thought that was a pretty good fit. I just have heard that these plants prefer to be rootbound & didn't want to over pot it.

Hopeful~ These are outside kittens, so they don't technically have a litter box... I'm wondering if that wouldn't solve my problem though. We live in the country, so I just assumed that they would have plenty of options when it came to "litter boxes", but maybe if I put one out, they'd use it instead of my plants. They aren't really nibbling on any of the plants. I do have a Hawaiian Ti Plant that they like to bat the leaves on, a couple of them have been shredded by little claws. :)

My PL was quite big when I got it. It's now in only a 6 in. pot, but I would say the plant is about 2-2 1/2 ft. tall (from soil level up) & spreads about as wide. Yes, my PL has been growing & blooming every since I got it, it seemed to never even notice the repotting.

Super~ Duct tape is a great idea! I'm just not sure how long it would stay sticky outside in our area. The plant is blocked from rain, but the heat may mess up the sticky-ness. I will have to give it a shot though. LOL, I have seen cats trying to get things off of their paws, it is quite amusing, but I usually end up feeling sorry for them & help them get whatever it is off. :)

Thanks for all the replies, they're greatly appreciated!

~Shannon

Since it is that big it probably does need a bigger pot.
Yes they like to be rootbound some and you are correct no more than 1 inch clearance from rootball to edge of pot. The roots might be wrapped around the inside so loosen them some when you repot will help it adapt better.

Drenching in a sink or bathtub doesn't always mean from the top. Thats why it was asked to be sure. Some people let them set in water completely covered then drain. You did state you take bottom saucer off so that is sort of implied bottom watering.

Perhaps the cats used to have a place to go before and now just found a similar substance.
There are those pokey spike strips that are put on roofs and ledges and other areas to keep birds off. Those would work. I saw them at Lowes today.