I can't speak for someone with CDIA's experience, but I can speak of my own personal experience doing a certification program in Cali (still completing...)

pros:
- Meet other people pursuing same goals; network
- Collaborative environment with feedback and support
- More stimulation and for many people, a structured environment helps

With that said, I come from an entirely unrelated background. So the classes I've taken (fundamentals) have been useful...up to a point.

Cons:
- I don't think its as rigorous as a degree...teachers seem 'meh' about the quality of student work. But I think its the case in any art school, it seems. This sucks because for the price you pay for each class, you'd expect the teachers to be whipping your ass...but no.
- Expensive
- Certificate doesn't mean you'll land a internship/job

In my experience, I do think employers like that you're working towards something...but its the portfolio they look at first. Always. I've been self-teaching myself for the past few months now, and its hard getting the motivation to keep pushing yourself without the stimulation you find in the classroom. But being in a classroom doesn't mean you'll produce great work. So you need to ask yourself: do I have the discipline to sit myself down and read through books/browse through forums, or do I need a structured environment?

The teacher teaches you the BASICS (which you can find online).
YOU have to figure out how to take the basics and make it AMAZING, in your own time.

You could always take 1-2 courses to feel it out at first.

Also, this forum is FILLED with useful information. USE it.

If you have money, sure, why not. A certificate program won't hurt.
If you don't, its totally doable to be self-taught in design. Discipline is key.