I also think that heavy curtains will do the trick. I also think curtains would be the longest lasting. The cheap blinds are made from PVC (now I find this out, after I filled my home with them
: ). The plastic degrades from the sunlight and cracks easily, not to mention off-gassing fumes. Also they really do let quite a bit of light in, and they collect dust like mad!
I usually make my own curtains--it's pretty easy if you can sew a straight line, you just fold the fabric over to make a tube at the top for the rod, then hang them up and mark where you want the bottom, and sew a hem. My Mom always seems to buy hers from the Pennys or Sears catalogs (usually polyester, though). Target has some nice curtains, Ikea too. Pottery Barn and Restoration Hardware have stunning heavy curtains in their catalogs if you can spend some $. Some Goodwills have unbelievable curtains for sale, too!
Good curtains will last for a really long time, just make sure they're machine washable and you won't need to take them to a dry cleaners.