Hard Decisions---Cortona, San Gim, or Arezzo???????

Okay we are staying in Florence for 2 nights and Siena for 2 nights. We REALLY want to see Cortona and also 1-2 hilltowns. We really like the hilltowns. We are travelling only by Eurail and I need to know firstly if I can reach all these hilltowns by train, and secondly which places should I FORSURE go to???? Any help is appreciated, thanks!

Ciao

Id say Areezo! its a nice town and less touristic than Florence.
for a hill town try - Monteriggioni - its fantastic and not far from Siena - reachable by bus...i dont think u can reach any hill towns by train.