Custom Yard Signs

We will have an open house and free blood pressure screening at my desk trying to find new customers. I need to get signs cheap, but decent is, does anyone have any suggestions or experiences with companies?
I do not want garbage, I'm in Michigan so it'll rain, but I need something special. Cheap is the key.

Thank you!

I got lucky with these guys:
http://www.dirtcheapsigns.com/

Here's a company in Wyandotte, MI, you can check with the Better Business Bureau exists (or ask a local estate agent who they use):
http://www.signoutfitters.com/

I hope this helps!