Say you set the card then activate Giant Trunade.....does that work?

Nope -- judging by the card text, it activates like a Normal Trap. Its effect isn't an alternate activation condition (Dark Coffin, etc), rather, you have to chain it to an effect that would return it just like you would chain Magic Jammer to a Spell card. So it has to be on the field for a turn.

No you cannot...it's basic Trap Card rulings...you cannot manually activate a Trap Card the same turn you set it unless it meets a certain requirement (like Kozaky's Self Destruct Button, Dark Coffin, Statue of the Wicked, etc).

In this case, you manually would choose to activate Map of Buried Treasure/Treasure Map in response to the activation of an effect (Monster, Magic or Trap) that would return it to your hand, but then game mechanics would prevent you since you just Set it.

So you would have to wait at least through your own turn in order to activate it.

Thanks.

I guess It's a bit of a risk then, If you can't play giant trunade the same turn you set....it's pretty useless.

It's hardly useless at all...it's to prevent it from potentially becoming too broken.