If I am attacking and roll 2 hits and 1 surge and the defender rolls defense for 2 blocks, can I still use the surge?

Yes, even if the defender rolled a Dodge result, the attacker could still use surges.

But keep in mind you can't trigger blast or cleave or impose any harmful conditions when the attack doesn't do damage.

Remember however that some surge abilities are only triggered if damage is done to the defender i.e. cleave, blast & bleed.

Edit: Beaten to it.

Remember however that some surge abilities are only triggered if damage is done to the defender i.e. cleave, blast & bleed.

Edit: Beaten to it.

Well, you can trigger them, but they have no effect unless you do damage. Maybe there will be something later that makes a distinction ala Lt Blout http://xwing-miniatures.wikia.com/wiki/Lieutenant_Blount

But you can always use an a surge to recover strain and i believe the probe droid can use a surge to recvover damage.

Not all abilities require damage to be inflicted to activate... just most (and specifically the conditions).