M.-
I have two boys, one is 5 1/2 and the other is 18 months. Both boys are capable at 18-24 months to know when they are pooping and peeing as well as tell you and tell you potty. I am expecting my third child in Dec. I would love for my youngest son to train earlier than my first but I am not expecting it.
In my experience and in talking to multiple moms who have boys, most boys don't really potty train until they are closer to 3 yrs. old. (Of course each child is different) I have heard of girls who train as early as 18 months.
It is good to introduce the potty and a praise/reward system for using it at 2 yrs. old. It is also a smart choice not to make it a big deal. I have seen moms who decided their children should be trained at 2 1/2 and they fought the potty training battle until their children were four years old. It is also my opinion that boys don't like to interrupt their play to use the bathroom.
My advice is to provide the tools for your son to use the bathroom. Get your husband to allow your son to see him going to the bathroom as often as possible. Praise and reward for the use of the potty. Encourage him with "look at these big boy underwear with Thomas (or his favorite character), when you start going potty you get to wear big boy underwear." Just don't make it an issue or it will take a lot longer to complete. Keep taking him to the bathroom to try as long as he doesn't protest every hour or so and sooner or later he will get the hang of it. We also used the "potty Elmo" toy for fun to help introduce the concept.
Good luck!