Like everyone else said, you can use whatever side you want. BUT, just so there are not surprises later, I would make a sample, using the batting you are going to use and see if the print shows thru, before you do a lot of piecing, etc. I have found that some prints show up stronger depending on the batting behind them. (It especially makes a difference between natural W&N, and white W&N.) So although you do not see the print when looking at the backside, it might show up once everything is put together. It happened to a friend of mine, and she was very disappointed with the outcome, after all the work she had done. Hope it works out for you!
Happy New Year to all !!