If you feed regularly (I read you must do it at least once every night) your character will remain mostly "normal", and you won't take damage from the sun.
Vampires can thus fast-travel safely if they feed well. Check out your character status screen to know in which "phase" your vampire is. A higher number will get you even more powerful attributes and abilities, at the expanse of sun damage and lower dispositions from NPCs.
~Dark Cupcake of the Sith