Also as long as I know croatia is NOT part of the schengen area yet (which I hear they plan to join 2015), I plan to go there as well for a week before going to Spain. WIth that if I have spent far less then 90 days (Im US citizen and no visa required for schengen area for less then 90 days) in the schengen area yet I go to croatia for say a week or a few days before going to Spain, would I have trouble going back into the schengen area? Are multiple entries possible in and out of schengen possible as long as I have not exceeded the 90 day limit?

Im aware that going out of the schengen area does NOT reset the clock.