Cynergy Cycles also rents Specialized road bikes. I don't know if they're the latest/greatest version though. I would guess that Helen's will let you take a Cervelo out for longer than 15 minutes if they think you're serious (don't know about an hour.) I've done a couple 10-15 minute test rides there.

As mentioned, you can also monitor the demo schedule of the manufacturer's you are interested in. They will let you take the bike out for an hour if you want to. I took a Trek Domane out for a 30-40 minute demo and it was nice not to have to worry about scratching up a brand new bike.