Well I called one Kinkos and was told they don't do backlit printing, then called another and was told she didn't know what button to hit on the register to get me a price..
Soooo
I opened up Superpages and found, right in my hometown a very friendly knowledgeable guy that prints on 7 mil backlit material.. and he's pretty cheap, 20 bucks for a one off marquee.
I'll let you know how it turns out, but I think I may have an alternative besides the chain stores for those folks in the Southern New England area. I'll let you know.