Hollywood... newbies catch a lot of flack around here. Some members don't react well to newbies coming in and asking a bunch of questions about stuff it has taken them a whole career to learn. They should probably just come out and tell that to all newbies when you apply for membership. Most of your questions can probably be answered by searching the forums. However, if you choose to ask the questions, be prepared to endure the flames.
So... the fact is, until you are generating TONS of coroplast sign business, it's probably not in your best interest to invest a ton of capital in the equipment to do it. Instead, invest in a piece of equipment that is versatile and can be used for a larger variety of projects.
We have a 54" Roland VP540 printer. The possibilites are limitless with a printer like this. Among a million other things, we can print to adhesive vinyl and apply it to coroplast (or any other substrate) for short runs of signs. We can produce virtually any size and any quantity a customer needs. However, at some point, it's not worth the time to do it in house. If a customer needs 100+ 18x24 coro signs, it ends up being cheaper for us to outsource it. So that's what we do.
Where...
The only merchant member I have personal experience with in coro printing... I-45 Signs in Houston. Lucky for us, they are just a few miles down the road! Lucky for you, they ship all over the US.
By the way, to save you a little heartache, if you simply post an introduction and tell everyone who you are and what you do, you will likely get a bit warmer of a reception. Oh, and since we are all in the printing business in some form or fashion, we HATE spelling and grammatical errors. Post with caution
Good Luck!
Andrew