I'd give yourself some time to adjust before you write off the Madone. Lighter makes a huge difference, but it's not necessarily automatic, especially when the geometry is a lot different.

One of my riding buddies is going through a similar transition. All summer she rode with us roadies on a 40 lb hybrid. Even though she struggled at times, we all kept telling her she didn't know how strong she was. So when she got a road bike, she was very discouraged that her pace didn't immediately improve. But she's sped up quite a bit on the new bike and continues to get faster as she gets used to it.

If you can average 18+ on hilly rides on a cross bike you're SUPER strong. I'd say give it time, but also talk to your PT about issues specific to your hip.