Welcome to All Things Plants, Deneen!
You might want to experiment a bit with self-watering versus "regular" pots/planters. I have flower boxes hanging on our deck railing, which is on the south side of our house; I could NEVER keep anything growing in them until I got self-watering planters, they have been a literal life saver!
I do agree that you're going to need to somehow protect the plants from the squirrels if they're visiting... maybe something as simple as some "floating row cover" would work for you. Cayenne pepper may also help deter them -- I've read that will help with keeping them out of the bird seed. I think DE is pretty much a deterrent for slugs (which I wouldn't think you'd have a problem with there, unless maybe if you dig soil from someone's garden to put in the planters), and I've heard of, and tried, using hair clippings to deter deer (didn't work that well here), but I wouldn't imagine that would be a concern, either!
Every year is a learning curve, no matter where we have our garden!
