When a power says "Each creature in the blast", does that mean my allies are hit by the attack too? I play a Control Wizard/Witch and almost all of my powers are blast and burst that target creatures.
Yes, it means enemies and allies
A being in the game world. Both adventurers and monsters are creatures. See also adventurer and monster. - Published in Rules Compendium, page(s) 310.
There are options for avoiding friendly fire while still laying down a burst/blast zone that includes friendlies
War Wizard's Staff feat lets you slide an ally out of the way before the attack goes off (if you are wielding an arcane implement). War Wizard Expertise applies a -5 to-hit modifier for burst and blast powers cast through a light or heavy blade against allies.