If you have it, Photoshop would be the best to use. If not, talk with a local printer such as Kinko/FedEx and ask them what they feel would be best. They will print directly to the vinyl and print from a large roll. They could possibly print both 10' sections at the same time and therefore save material and $$ for you. They also will put grommets in for you at each corner and every 2' across the top.

Just looked at the width you were thinking. At 36" the savings won't happen.