You can take the train to the CT from Florence. You don't need to drive to La Spezia, pay for parking, and probably drive back to Florence in the dark. Just search "Florence S.M.N." to "Riomaggiore" (or wherever you want to start). Make sure you know when the last departure back to Florence is, probably around 8/8:30 p.m. depending on where you board.

http://www.fsitaliane.com/homepage_en.html

I believe zones A & B of the ZTL have the same rules, although the hours could be slightly different but not enough to effect your plans.

I wouldn't stay at the Eden Rock unless you've been to Florence before and/or have little interest in seeing most of the sights in the city. Besides, the interiors look like any hotel anywhere. A better choice in that direction, IMO, would be Villa Michele in Fiesole. But in either case, if your exploring will be mostly to the south (Chianti, Siena, SanGim, Volterra, etc.), you'd have to circle around Florence twice.

http://www.villasanmichele.com/web/o...an_michele.jsp

The Villa Cora is much closer than both of those, very atmospheric and has faster access to the main highways.