If you learned to dive in Monterey, the dive park at Casino Point should be a pretty easy environment for you. (That is, I'm assuming since you learned in Monterey, that you understand kelp). It's a pretty easy to navigate environment, since it basically drops down slowly as you head directly away from shore.
If nobody is around to show you around, simply walk down the steps, enter the water, swim out about 20-30' to one of the buoys, and drop down the anchor line. That will put you in about 15-19' feet depth. Then simply swim a bit deeper, say to 30 or 40' feet. Assuming you're facing down slope, simply turn right, and swim for a while at a constant depth, taking in the sights. After a while, turn around and come back.
Oh: depending on the tide, when you enter the water off the steps, watch carefully where you are going. There is a large rock on the left hand side of the steps, a few feet into the water. you could bang your knee on it if you have bad luck, but if you're looking where you're going, you'll easily see it and avoid it.
You're basically in a big cordoned off rectangle, when you're in the dive park. Assuming you don't stray out of its bounds, at worst, if you surface in the corner, you'd have a bit of a surface swim back. There are a couple of features (wrecks and such) at various depths: you're likely to at least find someone on the shore who can tell you where you are, or I'm sure you can download a map of the park.
But navigation-wise, it's really one of the simpler environments you're going to encounter.