I get all of my vinyl from coastal business supply. Siser Easy Weed is great stuff and comes in a lot of different lengths. 5 yards is enough to last you several years. 1 yard is more than enough for eight sets of numbers. We do 15" wide rolls too.
They ship super fast and have decent prices. If I order on Monday, I'll have my vinyl by Wednesday or Thursday in Michigan.
http://www.coastalbusiness.com/easyweed.aspx