I made two hefes, both of which fermented in the 65-68 range with WLP300 yeast. Neither of them had very much hefe character, which was disappointing. My third was fermented at around 69-72 and had plenty of hefe character, especially banana. I also changed my recipe along the way though, so take my experiences with a grain of salt.
By the way, go look at homebrewer_99's recipe and advice, I consider him a hefe guru and he was largely responsible for my third hefe turning out as good as it did