That was easy!
You don't have to wait at all, no. You can get plants in there right from the beginning. They don't need to be in pots. Most people place stem based plants straight into the substrate, sand, soil or gravel. There are many different types of plants available, some of which are best tied to pieces of bog wood, stones etc, it's really dependent on the plant type and of course the look you're going for.
I know what you mean about the snail infestation. My first foray into snails were plant hitchhikers as well. I wouldn't at all say they were necessary, especially not the ones that breed at an exponential rate, but, there are some available which are actually rather nice looking. You can treat plant with copper based meds to rid them of snails, however, it's pretty bad for shrimp, if you decide to keep them, too.
My advice would be to start with very easy to grow plants from the Tropica 1-2-Grow range. They're specially grown in an non-snaily environment!