Going in May. Should we purchase before we go? If so, where is easy place to pick up? (flying into FCO)
If purchasing upon arrival is best, easiest place to buy? Thanks!
IMO no need to purchase before you go. they're available everywhere. Big info station right in Termini (the train station). I'm sure they're available right in the airport too but if not, probably the easiest is to just stop in the info center at the end of the train station and get it there.
http://www.romapass.it/p.aspx?l=en&tid=8
This should be what you are looking for.