Board Thread:General Discussion/@comment-173.228.204.187-20130519215336/@comment-6881629-20130520111920

You should only get attacked on sight (without Dawnguard DLC) if you haven't drank blood for a few days, try feeding. Otherwise the spell (or scroll) of calm may help.

As for Falion he has his daily routine like all npcs he maybe of doing something check his wiki page (linked above) if you still can't find him the fight with you may have messed that up waiting ten to thirty in-game days might fix it.