{2}, {T}: Exile target creature you control.

At the beginning of your upkeep, you may sacrifice Safe Haven. If you do, return each card exiled with Safe Haven to the battlefield under its owner's control.

The card has two abilities, the first is an Activated Ability (<Cost>:<Effect>) and the second is a triggered ability (<At/When/Whenever> <Condition>, <Effect>).  The first ability will only ever go on the stack when its owner has priority to play spells or activate abilities, announces activating it, and pays its cost.  The second ability, being a triggered ability, will always trigger when it's condition is met, though it is a 'may' ability so you can opt Not to sac it.  The two abilities also have something in common, they are what is called 'Linked Abilities'  That is they will only ever refer to each other.  If you use some convoluted method to give either ability to another creature it will Not tie in with any other abilities they may have.  If you give the First ability to a Duplicant with nothing imprinted you will Not get the bonus of having something imprinted to it.  If you give the Second ability to a Duplicant it Will return the creature if sacrificed.  The reason it will on the second ability is that it refers to 'Each card exiled with this' and not the 'Imprinted' card like the duplicant would use.

Knowing this info we can answer both questions:

1)Q. My question goes as follows: If I stack the abilites so that sacrificing the land returns the exiled creatures before the exiling, can I get that creature back in play if I get the land back in play (and sac it again)?

A. Because the second ability is a triggered ability with the trigger being the Beginning of your upkeep you must put it on the stack at the beginning of your upkeep before you have the chance to activate its activated ability.  You cannot manipulate the stack with this.  If you were to activate the ability in response to the trigger, the creature would be exiled, the sac trigger would go on the stack, you sac the land and the creatures return including the one you just exiled.  If the land leaves play some how before you can return the exiled cards you will Not be able to get it back with returning it or using another.  Whenever an object changes zones it is considered to be a new object with no memory of its previous existance.  This includes things that may have been exiled with that card before it changed zones.  As an example of this, if you had Safe Haven and Living Lands out and cast Cloudshift on Safe Haven, the Safe Haven would Not be able to return any creatures it exiled before the Cloudshift was cast, they would just stay in exile.

2)Q.  If I have two Safe Havens and exile a creature with one and sac the other Haven, will the creature exiled by the Haven NOT sacrificed be brought back into play?


A. No, this was pretty well answered with my reply to question 1.

Hope this covers all your concerns :)