It's rare for teens to read for fun unless they are really into literature. In other words, give your YA audience more credit. You can do whatever you want. Plenty of teens like Fitzgerald more than Hemmingway, so don't be afraid of description. However, a dragging pace is appealing to no one. Write what you love and let society classify it as YA or whatever. The only thing inherently off-putting is excessive length (approx 400+ pages), but once someone decides to open the book it's up to you to keep them reading.
I think teens want something they can relate to or escape to, that's my guess anyways. Like some kind of epic struggle with all odds stacked against them, see Harry Potter, Eragon, Gemmel novels, Twilight Saga and Philip Pullman.
